Radders Posted April 7, 2011 Share Posted April 7, 2011 After changing to 14 inch wheels on my Mk2 2000 saloon, (It was on 13's originally) I have tried two sets of different tyres but both of them make the speedo read about 10mph out. On the RBRR I used 185 x14, and on the recent HCR I had 195/65 x 14's fitted. I need to change the tyres soon anyway, so does anyone have any idea what size tyre would not affect the speedo reading? Thanks. Link to comment Share on other sites More sharing options...
CRAJ Posted April 7, 2011 Share Posted April 7, 2011 Standard tyres would be 175/80/13 (140mm of sidewall height), so 195/65/14 (126.75mm of sidewall + 12.7mm extra from the 1" bigger wheel diameter =139.45mm) would be an almost exact match for them. 185/80/14 (148mm sidewall +12.7mm = 160.7mm) would make the speedo a bit inaccurate!Has anything else been changed in the interim which may effect the speedos accuracy like a diff ratio change, overdrive % change?Colin. Link to comment Share on other sites More sharing options...
StagNL Posted April 7, 2011 Share Posted April 7, 2011 Play around with this for some ideas:http://www.kouki.co.uk/utilities/visual-tyre-size-calculator Link to comment Share on other sites More sharing options...
CRAJ Posted April 7, 2011 Share Posted April 7, 2011 699 wrote:Play around with this for some ideas:http://www.kouki.co.uk/utilities/visual-tyre-size-calculatorI like that, saves time with the calculator too :)Colin. Link to comment Share on other sites More sharing options...
Richard B Posted April 7, 2011 Share Posted April 7, 2011 or courtesy of Jameshttp://www.mintylamb.co.uk/?page=tyre.htm Link to comment Share on other sites More sharing options...
Radders Posted April 7, 2011 Author Share Posted April 7, 2011 CRAJ wrote:Standard tyres would be 175/80/13 (140mm of sidewall height), so 195/65/14 (126.75mm of sidewall + 12.7mm extra from the 1" bigger wheel diameter =139.45mm) would be an almost exact match for them. 185/80/14 (148mm sidewall +12.7mm = 160.7mm) would make the speedo a bit inaccurate!Has anything else been changed in the interim which may effect the speedos accuracy like a diff ratio change, overdrive % change?Colin.Hmmm......you've just reminded me, I had to change the nylon drive in the gearbox before the RBRR when the speedo packed up and just pulled one out a spare geabox I had laying around. Could this be a cause? The diff and gearbox haven't been changed in my ownership, but I dont know if anything was changed before? Link to comment Share on other sites More sharing options...
Radders Posted April 7, 2011 Author Share Posted April 7, 2011 699 wrote:Play around with this for some ideas:http://www.kouki.co.uk/utilities/visual-tyre-size-calculatorThat's brilliant. According to this, if I change to 195/60 x14's, I'll be spot on. :) Link to comment Share on other sites More sharing options...
CRAJ Posted April 7, 2011 Share Posted April 7, 2011 391 wrote:That's brilliant. According to this, if I change to 195/60 x14's, I'll be spot on. :)Are you sure about that? 175/80/13 to a 195/60/14 will give a 3.4% over reading on the speedo. Where as the 195/65/14 you had for the HCR will give a 0.2% over reading. According to StagNL comparison link.Colin. Link to comment Share on other sites More sharing options...
Radders Posted April 7, 2011 Author Share Posted April 7, 2011 CRAJ wrote:Are you sure about that? 175/80/13 to a 195/60/14 will give a 3.4% over reading on the speedo. Where as the 195/65/14 you had for the HCR will give a 0.2% over reading. According to StagNL comparison link.Colin.I was going by the mph comparison below. If you look at that the speeds of the two tyres are exact :-/ Link to comment Share on other sites More sharing options...
thescrapman Posted April 7, 2011 Share Posted April 7, 2011 SteveIf the drive cog was a different colour it will have messed up the speedo reading.by approximately 5% or 10% depending on whether you fitted one that had 1 or 2 more / less teeth.Was 175-13 the standard tyre for a Mk2 2000??I reckon you need a 195/65-14 as well.Unless that is an uncommon size, in which case get what is cheap!Just looked, it is a cheap size.You won't even have to go for Tyfoons, Jinyu's, or Ling-Longs to get a tyre for about £40.CheersColin Link to comment Share on other sites More sharing options...
Radders Posted April 7, 2011 Author Share Posted April 7, 2011 thescrapman wrote:SteveI reckon you need a 195/65-14 as well.CheersColinThats what's on there now, but its still out. :-/ Link to comment Share on other sites More sharing options...
FloydP Posted April 7, 2011 Share Posted April 7, 2011 Are the speedos all the same, I seem to remember that on the Gt6 the overdrive speedo is calibrated differently to the normal one and I wondered if the same was true of the saloons.If it's any help I've got a stag speedo you can have to see how that reads.Cheers,Floyd. Link to comment Share on other sites More sharing options...
sparky_spit Posted April 7, 2011 Share Posted April 7, 2011 thescrapman wrote:SteveYou won't even have to go for Tyfoons, Jinyu's, or Ling-Longs to get a tyre for about £40.Don't you mean Woo-Sung Dark Horse tyres? I had some of these (yes, they really are real tyres) on the back of a Beemer some years ago and they certainly lived up to their name. Link to comment Share on other sites More sharing options...
CRAJ Posted April 7, 2011 Share Posted April 7, 2011 thescrapman wrote:Was 175-13 the standard tyre for a Mk2 2000??ColinPretty sure it was prefacelift, as PIs had 185-13, post facelift on a 2000/2500TC it may have been 185-13 like the PI was.I think the problem is probably speedo drive related too.Colin. Link to comment Share on other sites More sharing options...
thescrapman Posted April 7, 2011 Share Posted April 7, 2011 sparky_spit wrote:Don't you mean Woo-Sung Dark Horse tyres? I had some of these (yes, they really are real tyres) on the back of a Beemer some years ago and they certainly lived up to their name.If you are feeling brave I have found "High Performers", which are probably a mis-nomer, as they are most definatley at the lowest end of teh price spectrum.Fancy some Sagitars, or some Debicas.Perhaps an "Ovation" when you go through a hedge backwards....Thing is they are only about a tenner less than the more well known brands.I know Mr Randle will tell us how good Michelins are, but I haven't seen him come up with any free samples for us yet... :-)CheersColin Link to comment Share on other sites More sharing options...
Radders Posted April 7, 2011 Author Share Posted April 7, 2011 CRAJ wrote:Standard tyres would be 175/80/13 (140mm of sidewall height), so 195/65/14 (126.75mm of sidewall + 12.7mm extra from the 1" bigger wheel diameter =139.45mm) would be an almost exact match for them. 185/80/14 (148mm sidewall +12.7mm = 160.7mm) would make the speedo a bit inaccurate!Has anything else been changed in the interim which may effect the speedos accuracy like a diff ratio change, overdrive % change?Colin.Ah, I read this wrong. I'll have another look. :B Link to comment Share on other sites More sharing options...
GT6 M Posted April 7, 2011 Share Posted April 7, 2011 i like ths onehttp://www.miata.net/garage/tirecalc.htmlin my mind, the moer you can get the tyre to give moer mph x 1000 rpms, the better.I just cant get enough, :-/ :-/ :-/ Link to comment Share on other sites More sharing options...
dazzer Posted April 7, 2011 Share Posted April 7, 2011 The speedos are pretty innacurate anyway on the big saloons reasonable up to 40 but way out at 70 + I think 'optomistic' is the key word. With regard to tyres sizes, from new to worn will also give you quite a noticeable difference if checked on a accurate trip. I've just run a route with a brantz trip after changing my tyres which were down to 'just legal'. I fitted the same size and make again Dunlop SP 85 gravel tyres 185/70/13s. The accurately marked calibration route has now decreased from 10.5 miles to 10.1 miles.Give it a couple of months and I'll be back to 10.5 miles with a bit of wear!CheersDarren Link to comment Share on other sites More sharing options...
Raider Posted April 8, 2011 Share Posted April 8, 2011 thescrapman wrote:I know Mr Randle will tell us how good Michelins are, but I haven't seen him come up with any free samples for us yet... :-)CheersColinI have come a bit late to this and quite right Colin, no free samples ;DFree advice though but it confirms pretty much everything said already.Our (Michelin) 1982 tech data book lists 175R13 as the correct fitment on 2000 mk 2s and 2000TCs.Static laden radius on the 175R13s 275mm, on 195/65R14s 277mm so yes, an excellent size equivalent which won't affect speedo readings.As an aside - I am running 185/70R13 Mich on my 2000 as I took them off one of my TR7s and they have an SLR of 273. The car handles fine and yes the speedo is wildly optomistic (although I know it has a 3.77 diff fitted instead of 4.11 which will have a big effect).Finally, yes do please quality tyres even if they aren't ours :) Link to comment Share on other sites More sharing options...
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