tomfpurves Posted March 12, 2018 Report Share Posted March 12, 2018 I am having difficulty accessing the mintylamb gearspeed calculator site http://www.mintylamb.co.uk Does anyone have a link that works?Alternatively if I replace my 155 15 XAS with 180 15 XAS what is the difference in speed at 5000rpm in top?I have a 3:7 to 1 axle Any help appreciated. Tom Quote Link to post Share on other sites
iain Posted March 12, 2018 Report Share Posted March 12, 2018 Tom this might help, you enter the two tyre sizes and this allows you to calculate the new speed. https://tiresize.com/comparison/ Iain Quote Link to post Share on other sites
Hamish Posted March 12, 2018 Report Share Posted March 12, 2018 I am having difficulty accessing the mintylamb gearspeed calculator site http://www.mintylamb.co.uk Does anyone have a link that works?Alternatively if I replace my 155 15 XAS with 180 15 XAS what is the difference in speed at 5000rpm in top?I have a 3:7 to 1 axle Any help appreciated. Tom Hi Tom Minty lamb is no longer available. The chap who ran it had internet hosting problems I understand. Many of the tyre comparison sites should give you what you need. H Quote Link to post Share on other sites
RogerH Posted March 12, 2018 Report Share Posted March 12, 2018 Hi Tom, will the difference in the width have an effect 155 x 15 - 185 x 15 !! do they have different profiles. Roger Quote Link to post Share on other sites
Alec Pringle Posted March 12, 2018 Report Share Posted March 12, 2018 Hi Tom, see Michelin website for outside diameter of the tyres - 630mm for the 155, 680mm for the 180 Link - http://classic.michelin.com/en/Classic-Tyre-range/XAS Agreed gross diameter is not quite the same as twice net rolling radius, and the relationship does differ ever so slightly between different sizes of tyre, but the margin is small enough to be effectively irrelevant for your purposes, or so I'd suggest. Cheers Alec Quote Link to post Share on other sites
tomfpurves Posted March 12, 2018 Author Report Share Posted March 12, 2018 Thank you everyone.Very helpful indeed.The two Michelin tyres are same profile.The bigger 180 15 is 2 kilos heavier and will propel the car 5.4 mph faster at the smaller tyres 90 mph.The actual width is 157mm for the 155 and 175 for the 180.I also compared the Avon CRZZ 175/70 profile tyre which is wider still at 182mm but actually has a smaller rolling radius than the smaller Michelin giving a speed of 89.3 mph at the 90 mph equivalent.It is also 3 kilos heavier than the 155 Michelin.I suspect for pure track or hillclimb use the Avon would be better(probably stickier) but not necessarily for road use and certainly not for wear. I am a loyal Michelin customer as in my professional career I found that they always had the best people and the greatest commitment to technological advance as well as the roundest highest quality tyres requiring lease balance weights etc. If I am to move up a size to 180s or the Avons then I will need 5.5 inch rims so total expense is significant. Again thanks for the help,greatly appreciated. Quote Link to post Share on other sites
John Morrison Posted March 12, 2018 Report Share Posted March 12, 2018 Hi Tom. I'm working from memory here but I didn't think Michelin ever made a 155 15 XAS. Anyhow as regards diamensions, 155 15 has a revs per mile of 834. IF you are looking at 180 15 XAS, which Michelin did make, think that was a dedicated Citroen Tyre, then teh revs per mile is 781. John. Quote Link to post Share on other sites
tomfpurves Posted March 12, 2018 Author Report Share Posted March 12, 2018 Hi John Thank you very helpful. I confirm I presently have 155 15 Michelin XAS on my TR3A and they are excellent tyres. Tom Quote Link to post Share on other sites
Alec Pringle Posted March 12, 2018 Report Share Posted March 12, 2018 Hi John, if you check out my link above, the web page tabulates XAS availability . . . . . including 155. Cheers Alec Quote Link to post Share on other sites
John Morrison Posted March 12, 2018 Report Share Posted March 12, 2018 Happy to stand corrected, it was a long time since I wasinvolved. John. Quote Link to post Share on other sites
BlueTR3A-5EKT Posted March 14, 2018 Report Share Posted March 14, 2018 (edited) I have an Excel spreadsheet that does the job. It came from an American website. I am not able to add it to this post some reason. If anyone wants a copy please PM me with your email address and I will send it to them. Peter W PS The htm file I have added did not work. Edited March 14, 2018 by BlueTR3A-5EKT Quote Link to post Share on other sites
rogerguzzi Posted March 14, 2018 Report Share Posted March 14, 2018 Hello Tom Try this one. http://endtuning.com/gearratios/ Quote Link to post Share on other sites
BlueTR3A-5EKT Posted March 14, 2018 Report Share Posted March 14, 2018 Found it http://buckeyetriumphs.org/technical/Calculator/road_speed_vs_engine_speed_calcu.htm Quote Link to post Share on other sites
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.