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Bigger Tyres - Steering geometry reset??

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Zeb View Drop Down
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    Posted: 01 May 10 at 23:25
Hi all

I have just fitted a set of 205/R14's but had my steering geometry set with 207/70/R14's on the bus which are 41mm smaller in diameter, is it necessary to get the geometry reset for even tyre wear with a 20,5mm height change ?

I hope not as I swap the wheels from summer to winter so will be going between 185/R14's and 205/R14's every year.

Cheers

Zeb
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Chappy View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Chappy Quote  Post ReplyReply Direct Link To This Post Posted: 02 May 10 at 11:24
Are you sure about that calculation Zeb? For 185/82 x 14 to 205/70 x 14 I'm getting 11mm smaller diameter....??
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Zeb Quote  Post ReplyReply Direct Link To This Post Posted: 02 May 10 at 13:56
Hi Chappy

Yes I'm sure I checked a couple of those tyre comparison sites, maybe my post was not so clear.

Old std size: 205/70/R14's    = 642.6mm
New bigger:  205/(80)/R14's = 683.6mm

So a delta of 41mm on dia or 20,5mm on ride height which is a 6.4% Increase, squeezing a little extra speed on those long motorway trips.

The VW option of 185/82/14's I use for winter are 658,9mm, 16,3mm bigger on diameter than the 205/70/R14's which were on my Carats when the geometry was set. (I edited this as I think you are right the 185 VW tyre has an aspect ratio of 82, I could only find 1 site to plug in this number but still not 11mm??).

Logic says if I was going to be really fussy I should get it set in the middle between the winter and summer tyres but you try explaining that in the local tyre fitting place!

I'm sure the handling is OK but having spent a small fortune on these Continental Vanco 2's I don't want to see them wear badly.

Cheers

Zeb


Edited by Zeb - 02 May 10 at 14:10
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Chappy View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Chappy Quote  Post ReplyReply Direct Link To This Post Posted: 02 May 10 at 16:24
Ah, got you.  I got confused with the tyre sizes.  I thought you mean the diff between 185/82 x 14 and 205/70 x 14.
 
So I agree - I get 41mm between 205x70's and 205x80's too. Big smile   
 
I generally use this tyre size calc - click
 
I guess the right answer is to get it checked and adjusted every time you change if needed.  But, as a compromise you could keep a really close eye on them to see if they're starting to wear, and if so get it changed.
 
I know that I wore a pair down to the canvas and wire on the inside of the tyre in 2000 miles because I didn't get the adjustment set - but that was after fitting -50mm springs.    
 
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Zeb Quote  Post ReplyReply Direct Link To This Post Posted: 02 May 10 at 16:57
Now I'm pissed off !

Word of warning to anyone with 50mm lowering kit.............don't fit tyres this size.

I was out messing around in a car park to make sure they were clear and they are not. They were rubbing the front mud flaps when braking heavily so I changed the clips and they were then fine.

Out for another test drive braked hard when cornering and it clipped the middle of the wheelarch and bent it outwards, what a nightmare. The body work is perfectly true everywhere except this.

I am tempted to put the standard shocks back on, at least then I hope the shock will bottom out before the tyres hit the bloody van.

Anyone running standard shocks (and Bumpstops) with a 50mm AVO kit ? I can't see any harm if occasionally the shock bottoms out as long as it is not over every little bump.

brick-yard info advises 60mm lower trim two ribs off the shocks, 45mm lower and standard shocks are OK. 50mm got to be worth a shot if it saves my wheel arches.

Cheers

Zeb


Edited by Zeb - 02 May 10 at 17:05
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Post Options Post Options   Thanks (0) Thanks(0)   Quote busbuddy Quote  Post ReplyReply Direct Link To This Post Posted: 02 May 10 at 18:03
why did you change the front tyres???
 
for your extra speed you only needed them on the back, just change the fronts back to what they were and your clearance issues are solved
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Chappy Quote  Post ReplyReply Direct Link To This Post Posted: 02 May 10 at 18:56
hhmmmmm  just checked your 205/80's against what I'm running.
 
I've got a 50mm AVO kit, chopped bump stops and billy shocks.
 
I'm running:
 
215/55 x 17 front
225/55 x 17 rear
 
The fronts are CLOSE... if I really stand on the brakes I can get 'em to catch.  Wheels are 17 x 7 ET 50 all round and the width (with a 20mm spacer) mean the fronts only clear the suspension by about 4mm.
 
This means I can't get the front wheels tucked under the arch any more, and the outer edge of the tyre is just about in line with the wheel arch lip.
 
Full lock and braking hard will catch too.  Any bigger would be problematic, so comparing your 205x80 to mine  - I can see why it's giving probs.
 
Bus Buddy's right - can you go back to smaller on the front?  'swot I did and it actually gives the van a bit of a 'meaner' stance in my view Cool
 
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Zeb Quote  Post ReplyReply Direct Link To This Post Posted: 02 May 10 at 19:42
They are 8mm bigger radially than what you have there Chappy but narrower than the 215's you have on the front so there must be very similar clearance to the arch. I should have just driven normally and kept my fingers crossed but was determined to check it out properly.....wish I hadn't.

I guess the only time I would brake with the steering in this position would be to avoid hitting something at the last minute, so hopefully not very often.

As far as smaller tyres on the front I think it is fine to go narrower but not much lower, not sure what options I have for this size or how much it would help the clearance. Yours are only 5,5mm smaller radially on the front than rear so barely noticeable.

If I got a pair of 195/80's they would be exactly the same size as your fronts Chappy but 16mm smaller than my rear's in diameter, won't that look a bit odd ? Not to mention another £140.

I agree it is an option Bus Buddy but It would be the slowest dragster in France if I put the 205/70's back on the front, I wanted to keep it all as original as possible so I went with all 4. I was daft to think that as they are fitted to syncro's as standard they would not be a problem for me, particularly as my bus is probably 3 inches or more lower than a syncro.

Thanks for your advice


Zeb




Edited by Zeb - 02 May 10 at 19:52
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