Another Spare Tyre Question
Submitted: Wednesday, Jan 06, 2016 at 10:44
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Frank P (NSW)
Hi All,
Calling on the collective knowledge of this great group...
My 2014 BT50 came with 265/65-17 Dunlop AT22 Grandtreks and a factory towbar.
I intend to run out those tyres on easy trips, but for outback
treks I will probably get 70 profile BFG All Terrains. My first spare, carried in the canopy, will also be one of those.
The issue is the second spare, which is the current OEM spare - a 65 profile Grandtrek. It is under the vehicle immediately forward of the towbar. There is insufficient room between the towbar and the diff housing to accommodate a 70 profile tyre, so I cannot upgrade it without going to the expense of getting a replacement towbar - an expense I'd prefer to avoid if possible.
My question is
If I had to use the Grandtrek second spare, it would have a different rolling diameter to the 70 profile BFGs. Bearing in mind the mechanical fruit in the BT50/
Ranger - stability control, traction control, etc - and given that the need to use the second spare might occur some hundreds of km from a repair
shop, what are the implications of the different rolling diameters over that considerable distance?
There is no LSD on the BT, just open diffs and traction control, etc and a locker on the rear which I presume I should not use. Unlikely to need it out there anyway.
Would appreciate your comments and advice.
Cheers
Reply By: Les - PK Ranger - Wednesday, Jan 06, 2016 at 11:28
Wednesday, Jan 06, 2016 at 11:28
Having the
Ranger, my OEMs were AT22's as
well, they are a pretty good AT tyre, strong.
They work great on rocky stuff and are excellent on sand, beaches or deserts.
The only place they will let you down a bit with the finer tread is mud / clay / wet slick tracks if caught on them.
From your description, and without rear locker operating, you should be fine to run slightly different rolling dias, as long as there's no chance for mechanical binding, it might just look a bit odd, perhaps handle slightly different / pull to one side if they are on the front ??
If I read right, you are going from 265/65/17 to 265/70/17 ??
If so, this is just 3.3% difference, not too much to worry about in your situ as described.
I used this little site here to compare sizes . . .
Tyre size calculator / comparison
Seriously though, outback trips if not in wet season, you wold be fine on the AT22s, that's what I'd do, rotate all through use each service, they can wear out evenly then you can replace the lot.
AnswerID:
594530
Follow Up By: Member-George (WA) - Wednesday, Jan 06, 2016 at 13:33
Wednesday, Jan 06, 2016 at 13:33
I agree with Les, I have Grand
Treks 265 65 R17 AT22 on 2 Toyota 4WD's, they are a great tyre and have never let me down, soft sand, gravel and
rock. Why change unless you are heading for the Victorian High country during winter. Cheers
FollowupID:
862967
Follow Up By: Frank P (NSW) - Wednesday, Jan 06, 2016 at 15:35
Wednesday, Jan 06, 2016 at 15:35
Thanks Les and George,
Yes, Les, 265/65's to 265/70's. You've eased my mind somewhat re the mild unequal rolling diameter.
I haven't had as much luck with Grand
Treks (on my previous tug, a 120 Prado) as you guys have apparently had, and hence my preference to change. But I will run these out rather than throw away tyres with useable life in them.
Perhaps I am being harsh on the Grand
Treks. My tyre management practices have changed as I have learned. Perhaps that has had as much to do with better tyre performance as the change of brand. But I still like the BFGs as an all-round performer for what we do, so when it comes time to change, that's probably the way I'll go.
Cheers
FollowupID:
862983
Follow Up By: Les - PK Ranger - Thursday, Jan 07, 2016 at 07:58
Thursday, Jan 07, 2016 at 07:58
Cool decision mate, even though I have mixed and matched tyres once (got 2 couple of Maxxis ATs on the front at 10k to try), and ended up buying 2 new AT22's at one point, I wouldn't be paying what they're asking in general for them again.
There are too many slightly more aggressive AT's out there that are less $, and should go the distance for me.
I have 4 new Federal Couragia ATs on the bus now, and 2 x 3/4 depth tread AT22's for spares.
Once they go I will think about the move to 7" or 8" wide 16" rims, then either fit 245/70 or 245/75 (+ 4.3% or + 5.5% rolling dia respectively), that size would suit me nicely I feel.
FollowupID:
863019
Reply By: The Bantam - Thursday, Jan 07, 2016 at 01:50
Thursday, Jan 07, 2016 at 01:50
In the 4wd market, I believe there is an over emphasis on getting bigger tyres.
Truth to tell, most mere mortals will get to most
places they want to go on near factory size tyres. ....... its not like modern cars come with narrow, dunlop road track majors on split rims.
The small increase in tyre size you are considering will give next to bugger all extra clearance, next to bugger all larger foot print and next to no real advantage.
You are better off sticking with your factory tyre size and making good tyre choices and using good tyre managment practices.
cheers
AnswerID:
594567
Follow Up By: Member - Blue M - Thursday, Jan 07, 2016 at 05:04
Thursday, Jan 07, 2016 at 05:04
Bantam,
I would have to agree with you on this one.
Cheers
FollowupID:
863016
Follow Up By: Les - PK Ranger - Thursday, Jan 07, 2016 at 07:51
Thursday, Jan 07, 2016 at 07:51
Yes, larger rubber is often just fitted to look better (and it does look 'meaner' in most cases), but can cause issues if not done right with offset / track etc.
I feel people use will dictate if their need for more clearance for more challenging track work is required, nothing like cruising over larger obstacles where you used to touch before.
Having stockies / no lift on for a while does help you become a better driver, pick lines better etc.
I loved the extra 47mm clearance the 265/75/16s gave (+9.7% rolling dia), but now back on stock 235/75/15s it's a whole lot better vehicle to drive.
Once I wear out these 6 tyres evenly through rotation, I'll be looking at 8" rims in 16", and fitting either 245/70 with just + 4.3% difference rolling, or 245/75 at + 5.5%, that will do me nicely long term.
FollowupID:
863018
Follow Up By: The Bantam - Thursday, Jan 07, 2016 at 11:30
Thursday, Jan 07, 2016 at 11:30
Remember folks ..... if you increase your tyre size by 50mm, even in theory you only get an extra 25mm of clearance ...... in practice once you account for the tyre being flat on the bottom and
airing down ya gona get about 15mm of advantage ....... thats not a big deal.
Going for a wider tyre or one with a more advantageous profile or tyre type is a different story all together.
cheers
FollowupID:
863038
Follow Up By: Les - PK Ranger - Thursday, Jan 07, 2016 at 11:36
Thursday, Jan 07, 2016 at 11:36
Mate, you lose the air down height on either tyre sizes, so you do get a small increased lift advantage with any larger rolling dia :)
I would stick to 70 or 75 profile, much better for traction when deflated and stronger in side walls from what I've seen, most have to be LT grade in the higher side walls.
FollowupID:
863039
Follow Up By: The Bantam - Thursday, Jan 07, 2016 at 12:21
Thursday, Jan 07, 2016 at 12:21
Like so many things these days .... these 65 profile tyres are all to do with producing fuel economy and carbon figures ...... who in their right mind would have a low profile tyre as a first choice for off road.
Dropping rim size and increasing tyre profile will get a better result off road even at the same diameter.
cheers
FollowupID:
863046