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#1. Wide tires and contact patch size? - from Rob
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Date: Mon, 12 Feb 2001 19:23:03 -0700 From: "Rob" <motor@cadvision.com> Subject: Wide tires and contact patch size? Okay Sean has started one this time :) >>the "amount of tire on the road" is NOT a function of the size/width of the tires. the size of the contact patches is mostly a function of the weight of the car, and has a little to do with air pressures. so, no matter that you think, or have heard, wider tires do NOT give you "more rubber" on the road. wider tires make for a short/wide contact patch as opposed to a long/thin one (which is good for traction) but wider tires do NOT make for larger contact patches.<< I think most of use try to squeeze the largest (width) tire we can under the fenders of our E36's but maybe it is in vain?. Has anyone ever tested, or been able to offer an educated guess on the actual handling grip/performance difference of a 235/40/17 vs 245/40/17 vs 255/40/17 ?. It is just about time for new rubber on my car and I'm considering going from 245/40 to 235/40 to gain back a bit of gearing advantage. If the 245's don't offer more grip in the corners then it makes more sense to me to buy the cheaper, lighter and faster (accelerating) 235's. Thanks, Rob
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#2. Re: [E36M3] Wide tires and contact patch size? - from Steve Hudson
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Date: Mon, 12 Feb 2001 22:00:43 -0600 From: "Steve Hudson" <shudson@io.com> Subject: Re: [E36M3] Wide tires and contact patch size? Take a look at Bob Tunnell's discussion of tires at http://www.tunnellracing.com/M3toESP.html Steve Hudson '97 M3/4 ----- Original Message ----- From: Rob <motor@cadvision.com> To: E36M3 <e36m3@bmw-m.net> Sent: Monday, February 12, 2001 8:27 PM Subject: [E36M3] Wide tires and contact patch size? > Date: Mon, 12 Feb 2001 19:23:03 -0700 > From: "Rob" <motor@cadvision.com> > Subject: Wide tires and contact patch size? > > Okay Sean has started one this time :) > > >>the "amount of tire on the road" is NOT a function of the size/width of > the > tires. the size of the contact patches is mostly a function of the weight > of the car, and has a little to do with air pressures. so, no matter that > you think, or have heard, wider tires do NOT give you "more rubber" on the > road. wider tires make for a short/wide contact patch as opposed to a > long/thin one (which is good for traction) but wider tires do NOT make for > larger contact patches.<< > > I think most of use try to squeeze the largest (width) tire we can under > the fenders of our E36's but maybe it is in vain?. Has anyone ever tested, > or been able to offer an educated guess on the actual handling > grip/performance difference of a 235/40/17 vs 245/40/17 vs 255/40/17 ?. > It is just about time for new rubber on my car and I'm considering going > from 245/40 to 235/40 to gain back a bit of gearing advantage. If the 245's > don't offer more grip in the corners then it makes more sense to me to buy > the cheaper, lighter and faster (accelerating) 235's. > > Thanks, > Rob > > > > > > ************************************************************* > List Commands > UNSUBSCRIBE - (in subject line) unsubscribes you from the mailing list. > DIR - sends a listing of files available in the list's GET directory. > GET filename1.ext,filename2.ext - sends the requested file(s). > > To issue a command/request to the server: > Send a message with the command you wish executed as the > subject of the message. > ************************************************************* > >
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#3. Re: [E36M3] Wide tires and contact patch size? - from Matt Henson
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Date: Mon, 12 Feb 2001 20:32:37 -0800 (PST) From: Matt Henson <hensonator@yahoo.com> Subject: Re: [E36M3] Wide tires and contact patch size? While it is true that the static contact patch is always the same area, it does change its geometry with tire width. A wide tire has a wider, narrower patch. And, under most conditions (not all..) this can result in better grip. How's that? Well, consider something like sidewall flex and camber changes with cornering. If the tire loses contact on the inside 2" of the rubber then this will be a smaller percentage for a wide tire. So it won't be affected as much by the deformation. Also, wide tires have smaller slip angles, which also improves dynamic traction other good things. I would also expect wide tires to have a less progressive breakaway due to those smaller slip angles (not a good thing). Now, I say that it helps traction in most conditions because, like Bob Tunnell says, the wide tire won't get as hot a narrow one for a given amount of energy entering the tire. This is mostly an issue for autoX and maybe street driving. For a track you'd typically want the tire that doesn't heat up as much so the wide one wins again. Personally I think that most M3 owners would appreciate the greater acceleration of the 235's. -Matt --- Rob <motor@cadvision.com> wrote: > Date: Mon, 12 Feb 2001 19:23:03 -0700 > From: "Rob" <motor@cadvision.com> > Subject: Wide tires and contact patch size? > > Okay Sean has started one this time :) If the 245's > don't offer more grip in the corners then it makes > more sense to me to buy > the cheaper, lighter and faster (accelerating) > 235's. > > Thanks, > Rob __________________________________________________ Do You Yahoo!? Get personalized email addresses from Yahoo! Mail - only $35 a year! http://personal.mail.yahoo.com/
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#4. Re: [E36M3] More tire for less weight - from Bob Dorchester
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Date: Mon, 12 Feb 2001 22:29:56 -0600 From: Bob Dorchester <rjdorche@concentric.net> Subject: Re: [E36M3] More tire for less weight The difference here is the tire, much more so than the wheel. Hoosiers are about 7 lbs lighter than any other street or R-compound tire (Yok A032R and BFG R1) I have owned. Others = 25 lbs; Hoosier road race compound = 18 lbs. The autocross tire must be a pound or two less! While I have never weighed Kumhos, I understand they are also in the 25 lb range. Btw, my Fikse FM5 (similar to the Mach V) 8.5"x17 are about 19 lbs, not a real lightweight wheel. The stock 7.5" 10-spoke cast wheels are about 20 lbs, and soft as butter. Bob Dorchester 95 M3 > In case anybody's interested, I just weighed a stock 7.5" M3 10-spoke wheel > with 225/45-17 Kumho V700 Victoriracer mounted, and an 8.5" Fikse Mach V > with 245/40-17 Hoosier DOT road racing tire mounted. Both tires are > balanced; Hoosier is new and Kumho slightly used (2 track days). Neither > wheel has center caps. > > 225/45 setup = 46.5 lbs > 245/40 setup = 39.5 lbs > > Granted the wider setup is $$$$ more, but I never expected a seven pound > difference per corner with less wheel, and less tire on the road! Just for > your amusement and cocktail chatter. > > Dave Hogg
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#5. Re: [E36M3] Wide tires and contact patch size? - from Bora Akyol
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Date: Mon, 12 Feb 2001 21:34:11 -0800 From: "Bora Akyol" <akyol@akyol.org> Subject: Re: [E36M3] Wide tires and contact patch size? Didn't 95 M3s like mine come from the factory with 235/40s? Bora
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#6. Re: More tire for less weight - from Steve
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Date: Mon, 12 Feb 2001 21:42:12 -0800 From: Steve <sgrigory@pacbell.net> Subject: Re: More tire for less weight I weighed an 8-inch IFG with a brand new 225/45-17 Kuhmo V700, about 40lbs. This was done unscientifically on a nice bathroom scale. I weighed me and the wheel, then weighed just me. The difference was about 40lbs. steve 95 M3
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#7. Re: [E36M3] Wide tires and contact patch size? - from Sean Hester
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Date: Mon, 12 Feb 2001 22:17:37 -0800 From: "Sean Hester" <seanh_race@hotmail.com> Subject: Re: [E36M3] Wide tires and contact patch size? > Okay Sean has started one this time :) > > >>the "amount of tire on the road" is NOT a function of the size/width of >the >tires. the size of the contact patches is mostly a function of the weight >of the car, and has a little to do with air pressures. so, no matter that >you think, or have heard, wider tires do NOT give you "more rubber" on the >road. wider tires make for a short/wide contact patch as opposed to a >long/thin one (which is good for traction) but wider tires do NOT make for >larger contact patches.<< > > I think most of use try to squeeze the largest (width) tire we can under >the fenders of our E36's but maybe it is in vain?. Has anyone ever tested, >or been able to offer an educated guess on the actual handling >grip/performance difference of a 235/40/17 vs 245/40/17 vs 255/40/17 ?. >It is just about time for new rubber on my car and I'm considering going >from 245/40 to 235/40 to gain back a bit of gearing advantage. If the 245's >don't offer more grip in the corners then it makes more sense to me to buy >the cheaper, lighter and faster (accelerating) 235's. no no no. wider tires DO help with traction. (in the dry) but it's not because of a larger contact patch. it's because that a short wide contact patch is good for dry traction. it has to do with pretty complex stuff like how the tire deforms as it rolls, as it bends due to cornering forces and all that "way too much physics for a family list" kinda stuff. but it's NOT becuase there's more rubber touching the ground. the area of the contact patch is constant. if you get tires that are twice as wide you get a contact patch that's half as long. notice that i said "in the dry" though. in standing water or snow, a long narrow contact patch is better for traction. (mostly for ability to get water out from under the tire) i didn't mean to imply that wider tires aren't good for traction. they are. and the wider the better. as long as you stay on dry pavement. _________________________________________________________________ Get your FREE download of MSN Explorer at http://explorer.msn.com
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#8. Re: [E36M3] Wide tires and contact patch size? - from Sean Hester
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Date: Mon, 12 Feb 2001 22:30:17 -0800 From: "Sean Hester" <seanh_race@hotmail.com> Subject: Re: [E36M3] Wide tires and contact patch size? >Personally I think that most M3 owners would >appreciate the greater acceleration of the 235's. blasphemy!!! bigger is always better! ;-P the fact that i tracked my M3 for years and years with tiny 17/7.5 wheels with 235/40 tires (even for the rears (shudder)) is just idiotic! what was i thinking?! on a more serious note. i race my rx7 race car in two classes. one allows 7 inch rims. one allow 8 inch rims. for the second half of last year i ran 215 hoosiers on the small wheels, and 235 bfg R1s (the old ones) on the 8 inch rims. the hoosiers are known to be the "stickier" tire, but even so, the larger wheel/tire combo with the less sticky tire had alot more grip. enough for a consistant 3/4 of a second in lap times. (which is alot) so... an inch of width makes a noticible difference. _________________________________________________________________ Get your FREE download of MSN Explorer at http://explorer.msn.com
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#9. Re: [E36M3] Wide tires and contact patch size? - from Sean Hester
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Date: Mon, 12 Feb 2001 22:34:29 -0800 From: "Sean Hester" <seanh_race@hotmail.com> Subject: Re: [E36M3] Wide tires and contact patch size? >Didn't 95 M3s like mine come from the factory with 235/40s? yes. 235/40 on 17/7.7 inch rims all around. and i never changed sizes. even for the track. _________________________________________________________________ Get your FREE download of MSN Explorer at http://explorer.msn.com
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#10. More tire for less weight - from Bill Lackey
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Date: Mon, 12 Feb 2001 22:35:33 -0800 From: "Bill Lackey" <btlackey@hotmail.com> Subject: More tire for less weight Although weight has a bit to do with performance, its not everything. Hoosiers are a much softer and faster tire than the Kumho's, Toyo RA1's, 032's etc by construction. Hoosier slicks are 2-3 seconds a lap faster than Hoosier DOT's, but do not weigh significantly less. Some compounds even last as long as DOT's(R50). Tire construction and compound probally have more to do with lap time than weight. Its not really a fair fight. Bill Lackey _________________________________________________________________ Get your FREE download of MSN Explorer at http://explorer.msn.com