auszookers.com
https://auszookers.com/forum/

Tyre Size
https://auszookers.com/forum/viewtopic.php?f=5&t=56591		 Page 1 of 1
Author:  Christina M [ Wed Sep 02, 2020 12:38 pm ]
Post subject:  Tyre Size
Hi guys,

I recently bought a 1997 SWB Vitara. It's currently running 2257016 tyres however I need to replace the tyres soon and I am wondering how big I can go? I have recently done a 2inch lift with Dobinsons GS shockers and coils to suit. Can I go as high as 2457516 or will that just not work?
Author:  Joe [ Wed Sep 02, 2020 1:09 pm ]
Post subject:  Re: Tyre Size
with a 50mm lift 225/75r16 or 235/70r16 would work, with 245/75r16 ya would need a 2 inch body lift for tyres that size
Author:  Gwagensteve [ Wed Sep 02, 2020 8:04 pm ]
Post subject:  Re: Tyre Size
Just to be clear, suspension lift does not assist in fitting bigger tyres. That's the single biggest myth in 4WDing.

A body lift does help with tyre clearance, but the first point of contact between tyre and guard on a Vitara is the trailing edge of the front wheel arch. As this area is basically vertical, a body lift doesn't really assist in adding clearance on that spot, but it can help in other locations.

A 245 75 is pretty close to the size of a 31 10.5, and they will require some cutting of the inner guard around the trailing edge of the front wheelarch. 245's will be a little bit baggy on stock rims too, which will exacerbate the tyre rubbing on the chassis.

There are other good reasons to add suspension lift to a Vitara, principally raising the front roll centre, which balances the cars handling, but fitting bigger tyres isn't one of them.

I would have thought a 225/75 would be a reasonable choice.

Many years ago I spent a lot of time messing with vitaras - carby 1.6 through to V6.
Author:  Joe [ Wed Sep 02, 2020 8:12 pm ]
Post subject:  Re: Tyre Size
Gwagensteve wrote:
Just to be clear, suspension lift does not assist in fitting bigger tyres. That's the single biggest myth in 4WDing.


Suspension lift made bigger tyres fit on my GV, come think of just about all the 4wds I've owned the tyres I've fitted have only fit because of the suspension lift without the lift tyres would rub all over the place.
Author:  Gwagensteve [ Wed Sep 02, 2020 8:39 pm ]
Post subject:  Re: Tyre Size
Joe wrote:
Gwagensteve wrote:
Just to be clear, suspension lift does not assist in fitting bigger tyres. That's the single biggest myth in 4WDing.


Suspension lift made bigger tyres fit on my GV, come think of just about all the 4wds I've owned the tyres I've fitted have only fit because of the suspension lift without the lift tyres would rub all over the place.


That's actually not true. It made them fit when the car was stationary, or it made them rub less in general use. Which is a bit like having a massively lowered car that's "fine" if you avoid speedbumps or that servo with the big steep entry tamp. However, if you move the suspension though it's full range of motion, the added clearance the suspension lift provides always vanishes, because suspension lift doesn't stop the axle moving into exactly the same spot it could before the lift was fitted. The "all over the place" the tyres would rub are exactly the places they'll rub when the suspension compresses the 2" you've lifted the car. That's not a lot of safety margin.

34" tyres fit a Sierra with no suspension lift (in the driveway, if you don't turn the steering) - like speedbump boi with the hekitk nissan - it's all about how much you're willing to compromise. What that's an example of is that it's not the suspension lift that's fitting the tyres, it's the owner avoiding certain situations.

The big problem with having tyres that don't fit "but don't rub too bad unless I really cross it up" is that you don't always get to choose the situation, and one day, you will accidentally jump the car, or jam it up really hard (often it's full lock reverse with the car fully flexed that will do it), and that's when tyres get cut up, guards get ripped off, inner guards peeled out, or, at worst, tyres jam badly enough axles break. I've seen it all happen when people run tyres that don't fit through the suspension's full range of travel.

Tyres fit when the car can be fully flexed to the bump stops without the tyres touching. I've probably flexed my car up 100 times over the last couple of years making sure my tyres fit under those circumstances, generally with the springs out so I can't kid myself I've got the tyres to fit only to find in the bush I'm putting more force into the suspension when the car is in motion than I can in the shed and the springs squish more, because I don't want to cross my fingers that I'm OK.
Author:  ZUZUKI [ Sun Sep 06, 2020 10:03 pm ]
Post subject:  Re: Tyre Size
I know we've been down this path many times before & the best way round it is to agree to disagree.
Don't you just love situations where theory doesn't quite match reality?
The theory is that as all the links, springs & bump stops are still in the same place, the suspension will cycle in the same arcs & if a tyre hit before suspension was fitted, then it will still hit afterwards.

The reality is that raised height suspension (and by doing nothing else) can allow larger tyres to fit that didn't prior to the suspension being fitted.
At the extreme end (as always, in the USA) they have been known to fit leaf springs with such an arch, that provide such a lift, that bigger tyres fit - the springs don't work very well as suspension, but that's beside the point.
With my SQ GV, 225/75R16 BFG A/Ts (the original - I'm going back years here) on stock alloys hit the top of the rear wheel arch - a lot.
Stock GV rear suspension is too lightly sprung.
After fitting an off the shelf OME suspension kit (35-40mm of raised ride height & 'stiffer' valved dampers / struts) - they didn't hit - much.
The only instance was rubbing if the car was loaded up for touring & I hit a 'dip' at higher (highway) speed than I should have. In this case, you could mostly 'choose the situation' that would cause it. I'm sure it would also hit if the car was accidentally 'jumped' - but white GVs don't jump.
I admit that this doesn't meet the definition of 'fitting' as in no tyre contact with the body or suspension under any circumstances & therefore is a technical RWC fail, but prior to suspension, I couldn't use the car the way I wanted to (tyre were getting cut), but afterwards, I could.

Cross axleing was fine. The practice that didn't match the theory, was that the suspension started its cycle from a different (lower) point. The arc that it moved through, was at enough of a different plane, that the wheels tucked into the well & not up, into the lip.

Probably 99% of instances / vehicles (unless in the USA), I would agree with you Steve, but with a GV, I'm convinced that you can drive on a larger tyre after fitting raised height suspension, that you couldn't drive on, on stock suspension.

Rgs, Michael
Author:  Joe [ Sun Sep 06, 2020 10:39 pm ]
Post subject:  Re: Tyre Size
Yes my point exactly, my swb vitara no way the 30x9.5r15 on 15x7 -13 would've fit without the lift and that had no rubbing at all
Author:  Gwagensteve [ Tue Sep 08, 2020 7:35 am ]
Post subject:  Re: Tyre Size
ZUZUKI wrote:
The only instance was rubbing if the car was loaded up for touring & I hit a 'dip' at higher (highway) speed than I should have.
I admit that this doesn't meet the definition of 'fitting'


Id say from that the practice exactly matches the theory. You had to avoid certain situations to prevent tyre contact. At that point it's all up to the individual how much compromise they're willing to endure to run the big tyre. You decided that was OK and that moving the rest point of the suspension that much made the compromise acceptable for you.

Many years ago we had a then newish V6 GV on a club weekend camping trip. Older owners, setting the car up for longer trips. (i.e relatively conservative) Bought 225/75/16's BFG MT's and an OME lift. This was it's debut trip.

First evening at camp and we're in there with hammers smashing the rear wheelarches away from the tyres which were getting destroyed on the guard lip. The owner probably drove around town for a couple of weeks believing the suspension lift meant his larger tyres would fit. I think in this instance it was dropping off the back of water bars that was fully compressing the back end and causing tyre damage.
Page 1 of 1 All times are UTC + 9:30 hours
Powered by phpBB® Forum Software © phpBB Group
https://www.phpbb.com/