kgh Posted June 29, 2009 Report Share Posted June 29, 2009 I took my MX5 Mk3 (NC) to Cadwell Park for a few laps (well 120+) on Friday. I kept the tyre pressures to 30-31psi, measured when hot, all round. When I changed the wheels on Saturday I found this:- The nearside front has large chunks missing fron the blocks to the right of the large groove whilst the offside front is fine. The rear tyres showed the same wear pattern but with smaller chunks missing. The tyres are Yokohama Parada Spec 2. Any thoughts? Quote Link to comment Share on other sites More sharing options...
CIH Posted June 29, 2009 Report Share Posted June 29, 2009 which direction is cadwell park ie; clockwise or anti-clockwise ? Quote Link to comment Share on other sites More sharing options...
kgh Posted June 29, 2009 Author Report Share Posted June 29, 2009 which direction is cadwell park ie; clockwise or anti-clockwise ? Clockwise. Quote Link to comment Share on other sites More sharing options...
Tony Posted June 29, 2009 Report Share Posted June 29, 2009 The tyres have delaminated?...... A combination of heat and lateral forces. Quote Link to comment Share on other sites More sharing options...
hms Posted June 30, 2009 Report Share Posted June 30, 2009 Can't see the pics. h Quote Link to comment Share on other sites More sharing options...
jon Posted July 3, 2009 Report Share Posted July 3, 2009 Were you understeering across the kerbs by any chance? Saw tooths can take chunks out of road tyres! Quote Link to comment Share on other sites More sharing options...
kgh Posted July 3, 2009 Author Report Share Posted July 3, 2009 Were you understeering across the kerbs by any chance? Saw tooths can take chunks out of road tyres! Not knowingly. The wear, front and rear, is in only one of the tyre blocks in the tread pattern and is in every one of these blocks. It seems unlikely that the kerbs could be so exactly aligned with the tyre tread. I suspect overheating is the culprit and I need to drive shorter sessions. Quote Link to comment Share on other sites More sharing options...
kgh Posted December 9, 2009 Author Report Share Posted December 9, 2009 My Toyo R888s are showing the same type of wear (without the delamination) so I decided to research the problem using my friend Google. The results seem to be that this type of wear is caused by the tread part of the contact patch (ie the bit between the sidewalls) distorting under the cornering forces. The distortion occurs because the sidewalls are very stiff. If the distortion results in a bulge this soon wears away giving the impression of a shallow groove worn away in the tread. Some of the R888 information I found referred to the "Groove of Doom". The cure is to increase type pressures and increase camber. The effect is apparently worse if the wheel width is at the lower end of the allowable range. I had found a list of recommended tyre pressures for the R888 based on the weight of the vehicle. So I set the pressures to 29psi cold and saw them rise to 34-35 hot. The Google searches suggest that the tyre pressures should be 40+ when hot. So I think I need to do this 1) Get the R888 refitted so I can swap them side to side (and get a bit more use out of them) 2) Change the alignment setup from Fast Road to a more aggresive track set up 3) Use higher cold pressures to achieve 40+ psi when hot. 4) Consider using 205/40/17 instead of 215/45/17 when I replace the tyres As always comments and suggestions are very welcome. Quote Link to comment Share on other sites More sharing options...
Tony Posted December 9, 2009 Report Share Posted December 9, 2009 We do this with slicks, but i've never experienced this on road/track tyres....... Any indication of the toe settings because this is also very different on slicks? Quote Link to comment Share on other sites More sharing options...
hms Posted December 10, 2009 Report Share Posted December 10, 2009 See here for Toyos setup info for spec Miata's on 888's: http://www.toyo.com/sites/default/files/im..._Guidelines.pdf They recommend 32 to 38 psi hot and suggest starting at 32pis and go from there. When I went to Mallory, with the 888's first outing, I had them at 30psi cold, don't know what that equates to hot. h Quote Link to comment Share on other sites More sharing options...
Bazza Posted December 10, 2009 Report Share Posted December 10, 2009 My Toyo R888s are showing the same type of wear (without the delamination) so I decided to research the problem using my friend Google. The results seem to be that this type of wear is caused by the tread part of the contact patch (ie the bit between the sidewalls) distorting under the cornering forces. The distortion occurs because the sidewalls are very stiff. If the distortion results in a bulge this soon wears away giving the impression of a shallow groove worn away in the tread. Some of the R888 information I found referred to the "Groove of Doom". The cure is to increase type pressures and increase camber. The effect is apparently worse if the wheel width is at the lower end of the allowable range. I had found a list of recommended tyre pressures for the R888 based on the weight of the vehicle. So I set the pressures to 29psi cold and saw them rise to 34-35 hot. The Google searches suggest that the tyre pressures should be 40+ when hot. So I think I need to do this 1) Get the R888 refitted so I can swap them side to side (and get a bit more use out of them) 2) Change the alignment setup from Fast Road to a more aggresive track set up 3) Use higher cold pressures to achieve 40+ psi when hot. 4) Consider using 205/40/17 instead of 215/45/17 when I replace the tyres As always comments and suggestions are very welcome. would a 205/40/17 not have a stiffer sidewall ? pressure calculations should also take in the distance, in the sprint series we were running r888s fairly low around 22-28 as there was little chance of getting them hot so relied on more surface area for grip if its not wet you can always turn the 888's around and go non directional Quote Link to comment Share on other sites More sharing options...
kgh Posted December 10, 2009 Author Report Share Posted December 10, 2009 We do this with slicks, but i've never experienced this on road/track tyres....... Any indication of the toe settings because this is also very different on slicks? The consenus on toe is to use zero toe all round. The stiffer sidewalls help the turn in and front toe out is not necessary. I would assume that 'zero toe' means zero dynamic toe. See here for Toyos setup info for spec Miata's on 888's: http://www.toyo.com/sites/default/files/im..._Guidelines.pdf They recommend 32 to 38 psi hot and suggest starting at 32pis and go from there. When I went to Mallory, with the 888's first outing, I had them at 30psi cold, don't know what that equates to hot. h Thanks. This is one of the articles I found. The Mk3 is considerably heavier than the Spec Miata and the standard Mk1 I have heard other MX-5 drivers saying that they intend to refit the tyres so that they can use them on the opposite side. This does suggest that they also experience uneven tyre wear but at the time I wasn't having this problem so I didn't look into it any further. I am ploughing a bit of a lonely furrow with the Mk3 on the track at the moment. There are a number of Mk3 race cars in development at the moment so I may be able to get help from them. Quote Link to comment Share on other sites More sharing options...
kgh Posted December 10, 2009 Author Report Share Posted December 10, 2009 would a 205/40/17 not have a stiffer sidewall ? pressure calculations should also take in the distance, in the sprint series we were running r888s fairly low around 22-28 as there was little chance of getting them hot so relied on more surface area for grip if its not wet you can always turn the 888's around and go non directional I was thinking that the 205/40/17 tyre would be a better fit to my 17x7 wheels than the 215/45/17 and would reduce the tread width and distortion. Track day distances are greater than sprints and tyre temperature does become a problem. I was thinking that I should swap the tyres side to side if it was dry (hopefully remembering to put them the correct way round before driving home) Quote Link to comment Share on other sites More sharing options...
Tony Posted December 10, 2009 Report Share Posted December 10, 2009 In the field pressure testing i cannot help with other than the nitrogen, actual mapping would be down to you... Zero toe on bump is very "flat-lined" and may be detrimental to results in the desire to preserve tyres. Did you know we have nearly finished developments of the fast-road/ track coilovers for the MK3 Quote Link to comment Share on other sites More sharing options...
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