DSC and Tire sizes

mlifxs · 07-19-2012, 01:30 PM

Hi folks, I've searched and found comments concerning DSC issues after people change their tire sizes. Wanted to throw my conclusions out there for comments/disagreement/corroboration. Thinking about my choices for new tires on my rear wheel drive E90 in the future. Thanks!

a. Difference (or ratio) between front and back tire diameters (or circumference) is the cause for DSC issues. Drastic changes in the difference (ratio), over stock difference (ratio) makes DSC think front is spinning faster/slower than rear, compared to stock. (True / False?)

b. Actual diameters for front and rear do not necessarily matter, again, it's the difference or ratio. If my OEM tires have a 25" diameter, front and rear, I could change my tires to 25.7" front and rear without DSC problems because the ratio of front and back (1/1) are the same in both cases. (True/False?)

c. Wheel and tire width should not cause issues, unless the change would induce higher levels of under-steer or over-steer (True / False?)

d. xi (4 wheel drive cars) are more sensitive to tire diameter ratio changes than non-xi (rear wheel drive). (True / False?)

e. Finally, assuming I'm on target with the front rear diameter ratio concept, does anyone know the ratio or percentage levels that would cause a problem for DSC? I'm guessing this would vary by car, but any info would be helpful.

Thanks again for any comments here.

mlifxs · 07-22-2012, 06:37 PM

a bump for your thots on this

Taipei-TT · 07-23-2012, 09:19 AM

I wish I could help you out more. The basic size of my wheels and tires is about the same after and before. I went from 225/45/17 to 235/35/19 and 265/30/19 with no dsc changes.

08*E90*328i · 07-24-2012, 11:19 AM

I know on my 350Z it only mattered if somehow the rear tires overall diameter was less than the front. Somehow people were matching up tires that had for example a 25.7" diam in front and a 25.5" diam in back. This would cause issues with Nissan's version of DSC. I know it isn't exactly the same, but I would think it would be similar.

richard in NC · 07-24-2012, 06:20 PM

I have heard the ratio issue. Can't say I know for sure.

mlifxs · 07-28-2012, 09:43 AM

Thanks for the comments so far.

Bumping this in case someone can confirm the questions here. I think it's a good thing to nail down (if it can be).

My OEM setup is 25" diameter front and back. When I change out tires, I'm considering 17" Michelin PSS. I may go square 245/40 with 24.7 diameter all around or stay staggered and go 235/45 and 245/45 which would put me at 25.4" front and 25.7" rear. I suspect both would work (with DSC) but I'd really regret making a mistake and having to switch out.

07-19-2012, 01:30 PM	#1
mlifxs Diamond Geezer 227 Rep 2,384 Posts Drives: Jet Black 2007 328i Saloon Join Date: Nov 2007 Location: Florida iTrader: (6) Garage List 2016 VW Golf Sportw ... [10.00]	DSC and Tire sizes - True or False? Hi folks, I've searched and found comments concerning DSC issues after people change their tire sizes. Wanted to throw my conclusions out there for comments/disagreement/corroboration. Thinking about my choices for new tires on my rear wheel drive E90 in the future. Thanks! a. Difference (or ratio) between front and back tire diameters (or circumference) is the cause for DSC issues. Drastic changes in the difference (ratio), over stock difference (ratio) makes DSC think front is spinning faster/slower than rear, compared to stock. (True / False?) b. Actual diameters for front and rear do not necessarily matter, again, it's the difference or ratio. If my OEM tires have a 25" diameter, front and rear, I could change my tires to 25.7" front and rear without DSC problems because the ratio of front and back (1/1) are the same in both cases. (True/False?) c. Wheel and tire width should not cause issues, unless the change would induce higher levels of under-steer or over-steer (True / False?) d. xi (4 wheel drive cars) are more sensitive to tire diameter ratio changes than non-xi (rear wheel drive). (True / False?) e. Finally, assuming I'm on target with the front rear diameter ratio concept, does anyone know the ratio or percentage levels that would cause a problem for DSC? I'm guessing this would vary by car, but any info would be helpful. Thanks again for any comments here.
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07-22-2012, 06:37 PM	#2
mlifxs Diamond Geezer 227 Rep 2,384 Posts Drives: Jet Black 2007 328i Saloon Join Date: Nov 2007 Location: Florida iTrader: (6) Garage List 2016 VW Golf Sportw ... [10.00]	a bump for your thots on this
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07-23-2012, 09:19 AM	#3
Taipei-TT Captain 26 Rep 642 Posts Drives: 2014 X3 2.0D Join Date: Oct 2009 Location: Canadian in Taipei iTrader: (0)	I wish I could help you out more. The basic size of my wheels and tires is about the same after and before. I went from 225/45/17 to 235/35/19 and 265/30/19 with no dsc changes.
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07-24-2012, 11:19 AM	#4
08E90328i Enlisted Member 0 Rep 41 Posts Drives: 08 328i e90 Join Date: Jul 2012 Location: Knoxville, TN iTrader: (1)	I know on my 350Z it only mattered if somehow the rear tires overall diameter was less than the front. Somehow people were matching up tires that had for example a 25.7" diam in front and a 25.5" diam in back. This would cause issues with Nissan's version of DSC. I know it isn't exactly the same, but I would think it would be similar.
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07-24-2012, 06:20 PM	#5
richard in NC Colonel 1242 Rep 2,601 Posts Drives: 2009 Z4 35i Join Date: Jul 2009 Location: Charlotte, NC iTrader: (0)	I have heard the ratio issue. Can't say I know for sure. __________________ 2020 X3M non-comp, Alpine White over black : Exec Pkg, ventilated M Sport seats, 20"s 2020 M2 Comp, Sunset Orange/Blk: Orange stitching, DCT, exec pkg, bicolor rims Gone '18 M550i, '16 X4 M40i, '15 M5, '13 X3 35i, '12 335is, '11 X5 50i, '09 Z4 35i, '08 550i, 06 X3, 06 650i, '02 M5, '99 540i
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07-28-2012, 09:43 AM	#6
mlifxs Diamond Geezer 227 Rep 2,384 Posts Drives: Jet Black 2007 328i Saloon Join Date: Nov 2007 Location: Florida iTrader: (6) Garage List 2016 VW Golf Sportw ... [10.00]	Thanks for the comments so far. Bumping this in case someone can confirm the questions here. I think it's a good thing to nail down (if it can be). My OEM setup is 25" diameter front and back. When I change out tires, I'm considering 17" Michelin PSS. I may go square 245/40 with 24.7 diameter all around or stay staggered and go 235/45 and 245/45 which would put me at 25.4" front and 25.7" rear. I suspect both would work (with DSC) but I'd really regret making a mistake and having to switch out.
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