Does changing the tire size affect anything?

Submitted: Friday, Nov 29, 2019 at 02:30
ThreadID: 139365 Views:1415 Replies:11 FollowUps:27
Hello everyone in the forum, the story is that my car is traveling with tire size 195 55R15. Now I want to change to tires size 195 60R15, what effect does the car speed, fuel consumption, braking wear...??? Please give me some advice, my tires are worn out.
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Reply By: Member - Core420 - Friday, Nov 29, 2019 at 06:27

Friday, Nov 29, 2019 at 06:27
With the slightly larger diameter (about 10mm) the wheel makes less turns to cover the same distance. So your speedo will be showing lower speed. ( about 10%). In theory brake wear could be higher because of the larger diameter, but there are so many other variables at play that it's impossible to say one way or another. Fuel consumption is similar; you will cover the same distance with less revolutions, but require a bit more effort to turn the wheel.
AnswerID: 628838

Follow Up By: RMD - Friday, Nov 29, 2019 at 08:03

Friday, Nov 29, 2019 at 08:03
Raises the vehicle height by around 5mm and the speed between 3 and 4 km, slower indicated, depending on actual tyre used, for the same road speed. Nowhere near 10% actually 1/3 of it.
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Reply By: Member - Bigfish - Friday, Nov 29, 2019 at 07:27

Friday, Nov 29, 2019 at 07:27
Why do you want to change tyre size if you dont know the effects?
AnswerID: 628839

Follow Up By: OBJ - Friday, Nov 29, 2019 at 09:15

Friday, Nov 29, 2019 at 09:15
He's asking what the effects are before he goes ahead, obviously.
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Follow Up By: Member Kerry W (WA) - Monday, Dec 02, 2019 at 22:35

Monday, Dec 02, 2019 at 22:35
He has a sense of adventure...
Kerry W (WA)
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Reply By: Hewy54 - Friday, Nov 29, 2019 at 07:30

Friday, Nov 29, 2019 at 07:30
Going to that new size will increase your circumference by 3.4%. This will mean that your speedo will be out by that amount (many read faster anyway, so this may mean that you actually get a more accurate figure)
A change of that amount will probably have little effect on the things you mentioned.
AnswerID: 628840

Reply By: Michael H9 - Friday, Nov 29, 2019 at 08:04

Friday, Nov 29, 2019 at 08:04
The larger diameter will mean your odometer will be reading 3.4% short as well. You fuel economy will appear to be worse even if it isn't because you'll think you're getting less kilometres per tank. If your car has a fuel economy read out then that will be fooled too.
AnswerID: 628841

Follow Up By: Michael H9 - Friday, Nov 29, 2019 at 13:51

Friday, Nov 29, 2019 at 13:51
I forgot to add, your car won't be showing as many kilometres on the clock when you trade it, and the time between services will be a little longer if you go by kilometres and not time.
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Reply By: eaglefree - Friday, Nov 29, 2019 at 08:15

Friday, Nov 29, 2019 at 08:15
You can go up or down two sizes legally from the original size.

My i30 Hyundai had , like many cars, an inaccurate speedo. Once I found how inaccurate it was (4%) I found the next tyre size up made it 100% accurate.

Google - tyre size comparison Australia

Advantages going to a larger tyre is-

You could be moving to a more common size hence cheaper
The side walls are bigger meaning softer ride
The tyres could last longer as will the engine marginally

Disadvantages is-

The tyre could run on body work esp turning and hitting a pothole
Tyres could be more expensive or harder to find or limited makes
The spare wheel might not fit in its wheel well
10mm higher vehicle might mean 20mm less ground clearance for the rear of the caravan
Tony

AnswerID: 628842

Follow Up By: RMD - Friday, Nov 29, 2019 at 13:42

Friday, Nov 29, 2019 at 13:42
With the 10mm higher vehicle, most caravans with rear set axle pivot position, means you may get 6 mm lower at rear of caravan. It cannot be more than the tyre rise. The principal of levers is in play there. If ball to pivot and pivot to rear of van is 3 :2 ratio then 6.6mm, which is about 1/3 of 20mm.
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Reply By: David I1 - Friday, Nov 29, 2019 at 08:18

Friday, Nov 29, 2019 at 08:18
From my experience this is what i have noted. I went up by 3.5cms in diameter, from a highway tyre to a LT construction. It then made my speedo accurate (with a GPS figure)at 100kph but my odometer out by 6% (ie 100 kilometres was in fact now 106 kilometres. The bigger diameter can effect your front end alignment, and I guess more mass may mean more breaking effort to stop (not that i noticed). However with the heavier tyres I did notice a slight increase in ltrs per 100kms. (about .1ltrs). Car sits higher off the ground, the tyres make more noise, and the steering is slightly more heavier. Also bigger tyres weigh more so you carrying capacity is also reduced by the difference in weight of the tyres in total, something people often forget.

If your change is only the size and not the brand/type then some of my findings would not be relevant.
AnswerID: 628843

Follow Up By: RMD - Friday, Nov 29, 2019 at 11:09

Friday, Nov 29, 2019 at 11:09
David
Maybe rethink your figures there. An increase in tyre size reduces the odo reading, not increase it at all, so the Odo reading will "lessen" by the percentage amount of tyre circumference differential. Therefore, 94 km recorded if a 6% difference of 100km travelled. Frack to Bunt?
The larger tyre size WILL NOT alter the front end alignment at all. The DIA % difference isn't a factor in reality BUT the increase in dia lessens retardation of same braking effort applied by brake booster/discs etc.
Tyre noise is a product of tyre design and construction, not because of a diameter increase.
A tyre with no more width and small increase in dia will actually make steering easier, not heavier, because of more tyre squirm ability and therefore steering easier. New tyres also ALWAYS are easier to steer than older tyres with less tread because of the tyre squirm is less with worn tyres. Absolute fact.
Bigger tyres CAN carry more, slightly heavier but not much with a 55 to 60 aspect tyre. low profiles can carry much less load, much less, so that is also incorrect.
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Reply By: David I1 - Friday, Nov 29, 2019 at 20:19

Friday, Nov 29, 2019 at 20:19
Sorry but 100kms on OD is really 106 actual as i said. Bigger diameter did effect front end, (well it did on my LR) and I had a before and after readings and adjustment to prove it. (not much but it did). Also can put more stress /load on bearings as well.As I said I went from Highway to LT AT tyres and there is a noise increase. And bigger circumference of tyre with the same brake pad /disc will cause more effort due to rotational effort.. It is easier to stop a 10cm wheel spinning than a 10 metre wheel, as there is more weight to slow down. (yes that is an exageration but only for demonstration purposes) In regards to weight I was making the point that from stock tyres on a 4Wd (which are usually Highway) to bigger tyres (even if only 55 to 60) and being LT construction will increase the weight of the car and so reduce carrying capacity of the vehicle. If they are the same tyre with the same construction then yes the weight increase would be small.
AnswerID: 628854

Follow Up By: Michael H9 - Friday, Nov 29, 2019 at 21:00

Friday, Nov 29, 2019 at 21:00
Yeah, I think you're both saying the same thing., if you're saying your odo is reading 100kms when you've actually travelled 106kms on the road. When I went up 2 sizes it was a 7% change so on the 5km freeway check area, my odo would be on 4.65kms which was pretty spot on and expected.
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Follow Up By: Blown4by - Saturday, Nov 30, 2019 at 00:21

Saturday, Nov 30, 2019 at 00:21
Davidl1: Maybe your wheel alignment changed in between changing tyre sizes not because of the size change but the many other factors that can affect W/A such as wear and tear, potholes, rubbing a kerb, running a wheel in deep sand while the other is still on a firm surface, etc, etc. Usually the increased load/stress on bearings is as a result of changes to rim offset, therefore changes to track rather than small changes to tyre size. If you go from 195/5515's to 35's then that is a different story. The reason braking efficiency decreases with increases in tyre diameter is not the extra weight, it is due to the simple physics of the distance from the point of contact with the road between the tyre and the centre of the axle with the same diameter brake rotor. If the distance between the point of contact of the tyre relative to the rotor diameter/position of the brake caliper is increased, it is in effect a longer lever hence it will be harder to stop the vehicle. If you went from Highway pattern tyres to LT A/T's it is not the size that caused additional road noise, it is as a consequence of the chunky tread pattern and heavier internal construction of the tyre, not its weight or size.
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Follow Up By: David I1 - Saturday, Nov 30, 2019 at 08:01

Saturday, Nov 30, 2019 at 08:01
I give up. I used my experience and I dont need "experts" to tell me what I experienced. Facts are facts and if what I experienced is not what experts think I did, then I MUST be wrong and my "feel" hearing and computer print outs of immediately before and immediately after the tyre change must mean the alignment equipment must have been all changed during the two tests. But I acknowledge the arm chair experts are all right, and my "on the road" assessment and equipment printouts are all wrong. Sorry my mistake. I apologise. I am wrong.
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Follow Up By: RMD - Saturday, Nov 30, 2019 at 10:38

Saturday, Nov 30, 2019 at 10:38
David
You change tyre TYPE not just the size so OF CORSE the noise will be greater. goes without saying if Highway to LT.
What you mentioned about wheel alignment cannot happen, impossible! However, if you had a reading taken, and then changed tyres and another reading taken, not sure of the sequence there but the aligner can "smoke and mirrors" the work task and yes make small adjustments to make it seem it was needed. They do it all the time. It is an industry norm. Printouts vary like the wind, you just have blind faith in them it seems.
If you don't have a depth of understanding of mechanical and other systems you can be easily deceived and therefore very sure of what you believe but it is not quite correct. Blown4by is correct, a slight change in section height will not affect bearing loading at all, but 35's will cause less braking effort to the road and side leverage of bearings increased. You do that all the time while cornering and don't realize, the cornering force is only relieved when the tyre adhesion to the road breaks away. I never mind if people state true facts and comments within the laws of physics or electrical laws. Nearly all who are challenged begin to point to others who try and correct the issue, not take on board what is being said. There are a few people on here who have vast experience in electrical and mechanic systems and have done so for all their life, which most don't. I agree with your summation you are wrong. The claim of armchair experts is often a comeback which the uninformed use to defend themselves.
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Follow Up By: David I1 - Saturday, Nov 30, 2019 at 11:19

Saturday, Nov 30, 2019 at 11:19
As I said RMD you are correct. Even though no front and rear end adjustment (I have a RR as you may know) was made between tyre changes as I said. So small adjustments were made between tyre changes that I did not see, even though I was watching what they did as it was a close friend who was doing the tyre change and I paid wholesale for the tyres and no charge for the FE alignment! So yes I must have been ripped off! I do know how to do FE alignments even on a car with air suspension which needs to be locked in position to do, as I have done them myself when I have need to, but then again I dont have the engineering qualifications, in physics and electrics, and my friend deliberately deceived me so he could justify putting a spanner to my car even though it was at no cost. I know what I saw and read. But then again I wear glasses and perhaps they were all fogged up, and so I made a complete mistake. All I can say is in MY particular case these changes were noted and recorded. As I said it was my experience with my car with the change in tyres both in size and construction. My experience was presented for information only, but as you say I am wrong, and you are so correct. Keep sitting in your armchair using your great theoretical knowledge to good use. It may work well in a lecture theatre but maybe, just maybe no so well in then practical world. Bye
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Follow Up By: Blown4by - Saturday, Nov 30, 2019 at 14:14

Saturday, Nov 30, 2019 at 14:14
David l1: I don't know why you are getting off your bike and so emotional about this mate unless you think forums are for you alone to express your opinions and challenging them or commenting on them is forbidden. No one is having a go at you mate. Pointing out other factors to consider about topics that are raised and comments that are made, if taken on board in the spirit with which they are offered, is how we all learn, because none of us knows everything, which is the great benefit of forums like these. A good mix of opinions given fair consideration helps to point us in the right direction and maybe bring to light some factors that weren't at first thought of or someone else may not be aware of. My comments didn't just relate to wheel alignment but mentioned tyre noise, increased wheel bearing load/stress and tyre diameter relative to braking efficiency. However I note you have only chosen to respond re the wheel alignment aspect which I can only assume is because to refer to the other issues raised would not suit your argument that everyone else, except you, is wrong. The simple answer is if you disagree with the opinions and engineering facts raised by others, there is no pressure to take them on board, so don't do so. The benefit of improving our knowledge though is that, none of us knows what we don't know.
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Follow Up By: RMD - Saturday, Nov 30, 2019 at 21:41

Saturday, Nov 30, 2019 at 21:41
Blown4by
Well said. You nailed it! I wonder if I arrived with my RR to his mate the aligner with identical rims with the LT tyres on them and simply unbolted the wheel nuts and replaced all wheels with the new set, WHY would the front end alignmemt change. That would mean David cannot ever fit the spare wheel in fear of the front end being out of aligment. I didn't know air suspension could tell the difference between tread styles. I live and learn.
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Follow Up By: Blown4by - Sunday, Dec 01, 2019 at 00:14

Sunday, Dec 01, 2019 at 00:14
He says he went up 35mm in diameter. Be interesting to know the replacement LT tyre size and whether a rim change with a different offset was involved. As is often the case with these issues, you only get half the story.
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Follow Up By: David I1 - Sunday, Dec 01, 2019 at 08:08

Sunday, Dec 01, 2019 at 08:08
They are compomotive rims and i went from a 20" rim to 18". They are designed exclusively for RR and D4's with the bigger front brakes. AFAIK the offset is the same. I have kept the old rims and tyres as i use them around town. I have done 40,000kms on the compomotives and the tyres are wearing evenly. However the OEM tyres with about 20,000kms and rims have worn a little more on the inside more than the outside ie neg camber. I am not overly concerned as my intention is to leave the compomotives on as to keep changing tyres/rims is a pain. Old tyre are 255/55/20 replacement are 255/70/18. Sorry tyre increase is only about 30mm when looking at tyre size calculators. I will not respond anymore as this is not what the OP asked. Only posted to shut up the know it alls. Cheers
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Follow Up By: RMD - Sunday, Dec 01, 2019 at 11:55

Sunday, Dec 01, 2019 at 11:55
David I 1
Your story has changed a bit and reveals more related info than first stated. If the OE tyres rims had worn a little on the inside, and now the replacements do not, YES, YES, YES you would need an alignment BUT, the need for alignment is because of wear pattern, not because you changed rims or tyres. Whether the rims are compomotive and exclusive or from austral wheel makers is not relevant as is the brake size. You said the rims are "the same offset, ASFAIK". Well! If I were changing rims I would definitely want to know if they were the same OR not. That can change things, regarding steering, bearing stress and load on alignment points and stability control. Probably the same offset though. Changing from one set or rims to another is only 15 mins work at the most if you are competent. Not an issue for many, as we change them from roadies to track rims/tyres when required. The two sizes you mention are 50mm bigger, not 30mm as stated. If your vehicle has independent rear then they nearly ALL have negative camber and wear the insides of the tread most of their lives. If rotated to front, that would indicate to an aligner the front needed correction. On the aligner they probably saw it didn't. Were you aware of such possibilities?
Simply needing to end a robust debate indicates you are not open to reality.
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Follow Up By: David I1 - Sunday, Dec 01, 2019 at 19:45

Sunday, Dec 01, 2019 at 19:45
They are not 50mm bigger read the rim size! This is why I stop posting as people do NOT READ my posts and understand what I say and then make stupid assumptions based on incorrect facts.I have just checked the offset with Compomotive and its the same. As I said the Compomotives are made especially for LR D4 and RR sport with the larger front calipers, and have the load capacity for the vehicles mentioned. Reality is what I experience not what you think I should be experiencing, hence all your views and opinions are theoretical as they do not seem/appear to align with what I have experienced and also backed upto some degree by documentation. I know i broke my rule on my last post but I just have to keep correcting people who do not/cannot read/understand/comprehend what I post up.
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Reply By: Bob Y. - Qld - Friday, Nov 29, 2019 at 22:29

Friday, Nov 29, 2019 at 22:29
FYI, there is a useful tyre size calculator/comparison on EO.

Go to Home, then Learn & click on Vehicles. It’s at top left of the page.

Bob

Seen it all, Done it all.
Can't remember most of it.

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Reply By: 9900Eagle - Saturday, Nov 30, 2019 at 12:02

Saturday, Nov 30, 2019 at 12:02
Alan, simple answer is. Fuel consumption will probably go up between .5 to 1 litre per 100k.

Speedo is easy fix, just use a gps and note the difference on your speedo at 40kph, 60kph, 100kph and 110kph, or do what I do and just drive using the gps as my speedo.

With that change in diameter I wouldn't worry about brakes.

AnswerID: 628872

Reply By: Dave B18 - Saturday, Nov 30, 2019 at 19:46

Saturday, Nov 30, 2019 at 19:46
Changing tyre sizes on a modern vehicle is stupidity from an engineering point of view. Modern vehicles are tuned machines from engine to tyre sizes for optimum reliability and performace.
Definitely not a smart move to change tyre sizes.
AnswerID: 628894

Follow Up By: Blown4by - Sunday, Dec 01, 2019 at 00:05

Sunday, Dec 01, 2019 at 00:05
Equally stupid from a legal standpoint too if the replacement tyres are not one of the optional sizes listed on the tyre placard. Changing tyre sizes outside the parameters that the Electronic Stability Control was designed to operate with may not only affect vehicle handling/safety, may be illegal, may void vehicle insurance and leave the owner exposed to possible civil action in the event of a serious accident.
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Follow Up By: Member Kerry W (WA) - Monday, Dec 02, 2019 at 22:45

Monday, Dec 02, 2019 at 22:45
So - has anybody asked Alan D14 what vehicle he drives and what he plans to trverse, where he lives - Does he live in a city?? Are the bigger tyres only for looks?? - Seems better to keep the vehicle in his garage than risk doing what most people do when the want to improve the offroad ability of the vehicle - so much thinking ...
so little exploring...
Kerry W (WA)
Security is mostly a superstition. It doesnt exist in nature. Life is either a daring adventure or nothing.
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Follow Up By: eaglefree - Tuesday, Dec 03, 2019 at 00:13

Tuesday, Dec 03, 2019 at 00:13
Are you asking him now Kerry?
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Follow Up By: Member Kerry W (WA) - Tuesday, Dec 03, 2019 at 00:33

Tuesday, Dec 03, 2019 at 00:33
Nope! - eaglefree not that interested - just noticed a lot of speculation and nobody asked the original poster any questions - was wondering if anybody really helped him out...or just scared him off
Kerry W (WA)
Security is mostly a superstition. It doesnt exist in nature. Life is either a daring adventure or nothing.
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Follow Up By: eaglefree - Tuesday, Dec 03, 2019 at 07:36

Tuesday, Dec 03, 2019 at 07:36
It’s really easy entering a discussion being critical of every poster that has attempted to answer the OP, toss a rock at them all and say “I’m not interested”. Add to that, you aren’t even asking the questions to the OP that you criticise everyone else of not doing.

Most amusing.
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Follow Up By: Member Kerry W (WA) - Tuesday, Dec 03, 2019 at 09:31

Tuesday, Dec 03, 2019 at 09:31
Even far more amusing eaglefree (not your real name I assume) is that I didn’t follow up on “your” post or any other - yet here you are making incorrect assumptions and being smug - sorry but your reply (and hiding behind another name) says a lot more about you than it does me!

I’ll spell it out - just in case it’s lost on you.... it seems you didn’t get what I actually wrote - I didn’t “reply” to the OP’s question at all - I “followed” up to this particular post -big difference - maybe I generalised a bit following up to you but you will notice I did not imply that your post or any other was not helpful just this “one” - some posts are so PC these days and someone needs to call out the fun police on occasion - I’m an old school adventurer so I remember what freedom really feels like ( we were also taught comprehension at school).... read the original follow up carefully again before you respond ??
Kerry W (WA)
Security is mostly a superstition. It doesnt exist in nature. Life is either a daring adventure or nothing.
-Helen Keller

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Follow Up By: eaglefree - Tuesday, Dec 03, 2019 at 09:48

Tuesday, Dec 03, 2019 at 09:48
Kerry you are full of judgements based on assumptions.

I usually put “Tony” after a post, you can check out my posts in this thread, no less open than “Kerry W” which doesn’t reveal any greater information besides if you were more knowledgeable you’d know that when you join a forum you are asked a user name that doesn’t need to be your real name- and forums with the same program often share the same user name. So throw another stone.
Your post was unnecessary, non productive and you didn’t assist the OP. I for one will call out people that have no other objective but to muddy the waters.
Oh, you do have good comprehension but don’t comprehend.
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Follow Up By: Member Kerry W (WA) - Tuesday, Dec 03, 2019 at 10:02

Tuesday, Dec 03, 2019 at 10:02
Bit touchy there tony - remember - “I didn’t post” you obviously didn’t read my original follow up as suggested - I’ll leave it here as I have far more respect for this forum - I’ll let you have the last say if you need to.
Kerry W (WA)
Security is mostly a superstition. It doesnt exist in nature. Life is either a daring adventure or nothing.
-Helen Keller

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Follow Up By: Dave B18 - Tuesday, Dec 03, 2019 at 18:35

Tuesday, Dec 03, 2019 at 18:35
Kerry W doesn't matter what he does with his vehicle, changing tyre sizes from OEM is engineering dumb if you want longevity and reliability from your vehicle. If you need to go in terrain a standard equipped 4WD won't, then start looking for to vehicles that are built to do the job.
Fact is many spend a small fortune on wanky suspension lifts and upgrades and other fruit and all for show, and seldom to never use the extra equipment. Having travelled the back blocks of Australia for all the time we have, never have needed other than standard size tyres - and never been overloaded or had break downs.
Soon as you fit larger tyres, you increase the designed load on all the mechanicals. Why do you think manufacturers won't warranty vehicles with increased tyres sizes or Blue Plated GVM or GCM upgrades.
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Follow Up By: Michael H9 - Tuesday, Dec 03, 2019 at 20:23

Tuesday, Dec 03, 2019 at 20:23
This guy has said he's thinking of going from 195/55/15 to 195/60/15. That's bugger all really and possibly in range on the tyre placard. We're talking a Mazda 323 or similar.
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Reply By: swampy - Saturday, Dec 07, 2019 at 20:30

Saturday, Dec 07, 2019 at 20:30
HI
Diameter can vary 3%
Why speedo accuracy . Most speedos will read 5km/h under and up to 2km/h over
AnswerID: 629014

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