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The mkiv Supra Owners Club

Tyre and Wheel upsizing - what goes on other than weight.


rider
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Go Wider tyres

Pro – Aesthetics, better traction at low speeds and launch

Cons - Cost, offset issues, will hydroplane before an equivalent standard tyre will. Noisier. Higher wear.

 

Everyone loves wide tyres but unless you are doing drag race with launch starts they probably don’t add much beyond aesthetics. Large offsets to accommodate the widest possible tyres has the potential to raise stress on drive components. Once a car has attained moderate speeds increasing tyre width has no appreciable impact on road friction.

 

Go Bigger wheels

Pro – Aesthetics, fitment of larger brake discs and callipers, reduced coefficient of friction

Cons – Heavier (same wheel alloy) which will slow 0-60mph time. A harsher ride with lower profile tyres than the OE standard.

 

Bigger wheels will reduce tyre friction due to pad pattern of lower profile tyres by around 5% per inch upsizing. At high speed cruising a standard car can consume 20HP just overcoming the tyre friction that turns to heat. So bigger wheels are going to generate less heat and has the potential to save fuel with a compromise of a harsher and noisier ride.

 

Tyre tread

Pro – Aesthetics, traction, water displacement

Con – Road noise

 

Tyre tread depth is the single largest contributor to stopping distance. Testing in the wet of a various depth tread tyre showed a 1mm tread tyre has a stopping distance 60% further than a new 8mm tyre in the wet. The tread pattern is a major contributor to road noise. Less so on traction as the tyre compound softness has a far greater impact upon that.

 

Tyre pressure

A 1 bar under inflation raises the coefficient of friction by around 30%; generating a lot more heat potentially leading to a tyre failure.

 

Summary – Leaving aside the aesthetics. Wider tyres are a bolt on for drag strip days on a dry strip to get the best launch traction and best possible 0-60 time. They wont help the 30-100 time though. Bigger wheels are a good upgrade if you need or want bigger brakes so long as you can keep the weight increase to a minimum you’ll then save fuel and generate less heat but have to accept greater road noise and a harsher ride. Tyre wear is the major factor affecting stopping distance, much more than bigger brakes which only address fade through repeated use. For everyday road use stock wheel/tyres makes sense for comfort of ride and noise levels.

 

Nothing really surprising but its always useful to align data to preconceptions and it details the compromises that often arise from applying track and drag day solutions to what is for most just an everyday or occasional day road car that will never see a race track. The solution of course is to have two sets of wheels and tyres to cover every occasion.

 

Someone once wrote that the best riding Supra is one on 16 inch wheels with 50 profile tyres. I have recently purchased a set of 16's so I really should check that out for myself. Some copy and paste links for anyone wishing to do some reading around the subject.

 

http://publications.lib.chalmers.se/records/fulltext/200040/200040.pdf

 

http://doc.utwente.nl/102225/1/Bezemer,%20Wijnant,%20de%20Boer%20-%202016%20-%20Internoise%20-%20Tyre-road%20noise%20measurements-%20influence%20of%20tyre%20tread%20and%20road%20charcateristics.pdf

 

http://www.caranddriver.com/features/effects-of-upsized-wheels-and-tires-tested

 

http://www.etyres.co.uk/tread-depths-distance/

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I found an old thread but it doesn't say if they're OE 16's or 17's but either way OE wheels are way heavier than any of the WORK wheels listed

in the link

 

http://measurespeed.com/work-rims-wheel-weight

 

http://www.mkivsupra.net/vbb/showthread.php?204765-List-of-stock-items-weights

 

Stock front wheels (no tyres): 22kg

Stock rear wheels(no tyres): 24kg

Edited by Dnk (see edit history)
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My aftermarket Weds SA-15R's are 2kg lighter at 18" than the stock 17's just for the alloy. The Weds are ~9kg each and the stock 17's are about 11-12kg. I'm not much wider than stock, just enough to improve traction from slow rolling starts (still break traction from a standstill).

 

http://www.mkivsupra.net/vbb/showthread.php?62606-Stock-17-quot-wheel-weight

 

The ride is far more supple on my winter 17's but I don't find the 18's a bad daily compromise at all. I also think the 18's look better.

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