Does changing the tire size affect anything?

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.

He's asking what the effects are before he goes ahead, obviously.

He has a sense of adventure...

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.

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.

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.

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.

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.

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.

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.

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

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.

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.

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.

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

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.

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.

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.

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...

Are you asking him now Kerry?

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

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.

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 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.

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 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.

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.