Holyzeus Posted March 28, 2007 Share Posted March 28, 2007 I know it'll have been covered before but i couldn't find it in a search, how far out will my speedo be with 35" simex's over norm? TIA ,Bal Quote Link to comment Share on other sites More sharing options...
BogMonster Posted March 28, 2007 Share Posted March 28, 2007 What tyres are fitted for a start. Since the circumference of a tyre is pi x diameter and the rolling circumference is what affects the speedo, you can work it out as the ratio of the old and new sizes anyway so if you have 32" tyres fitted and wish to go to 35s, then the speedo will read 32/35 x whatever so instead of 50mph it will read about 45.7, and so on. Quote Link to comment Share on other sites More sharing options...
LandyManLuke Posted March 28, 2007 Share Posted March 28, 2007 Best bet is to beg/borrow/steal a GPS, and take that out with you, before and after. The speedo normally isn't that accurate to start with. This page is a useful one. Quote Link to comment Share on other sites More sharing options...
Holyzeus Posted March 29, 2007 Author Share Posted March 29, 2007 Thanks for the replies but... Bogmonster, i have put on the post that they are 35" simex's after that you have lost me! . Landymanluke, good link have seen these before but i dont know original tyre size for a 90 also these calculators dont allow you to enter 35" only 235 etc Quote Link to comment Share on other sites More sharing options...
Guest dew110CSW Posted March 29, 2007 Share Posted March 29, 2007 90's original would be 205x70 IIRC. Quote Link to comment Share on other sites More sharing options...
JST Posted March 29, 2007 Share Posted March 29, 2007 take for example: 90 original 205R16 as base 1. move upto 235/85 or 7.50R16 then out by roughly 10% on 205 speedo pinion 2. move upto 255/85 (33" high) then out by 20% roughly on 205 pinion speedo 3. move upto 35" tyres then 30% out on 205 pinion speedo Some 90s eg those with alloys and 235/85 or 265/75s from factory will have the 110 speedo pinion fitted therefore from above 1. LR accurate 2. out by 10% with 255/85 on 235/85 pinion (for 235/85 read 265/75 or 7.50R16 they all use the same pinion) 3. 35" tyres out by 20% on 235/85 pinion. Note LR accurate means accuracy LR build in (or out which can be +/-10%) mine for example on 255/85s with 235/85 speedo pinion fitted is GPS speed bang on. its then 10% low with 35" simex on. eg reads 54pmh when your doing 60mph. Quote Link to comment Share on other sites More sharing options...
Holyzeus Posted March 29, 2007 Author Share Posted March 29, 2007 Many thanks, so to check my maths and understanding of the above with 35"s.......... 49 indicated will be 70 42 " " " 60 35 " " " 50 ? although to be sure due to LR build tolerences i need to check using a GPS? Quote Link to comment Share on other sites More sharing options...
JST Posted March 30, 2007 Share Posted March 30, 2007 with a 205 pinion i reckon on 35s 35 + 30% = 45mph the % is on the speedo reaing not on the speed. if that makes sense, i woudl check with GPS, how do you knwo that your not on a 235/7.50 pinion? Quote Link to comment Share on other sites More sharing options...
JST Posted March 30, 2007 Share Posted March 30, 2007 somestuff on speedos and rpm for speeds/pinion etc LRA Overdive/1.2 box thread Quote Link to comment Share on other sites More sharing options...
Holyzeus Posted March 30, 2007 Author Share Posted March 30, 2007 Thanks James Quote Link to comment Share on other sites More sharing options...
JimAttrill Posted March 31, 2007 Share Posted March 31, 2007 How long do those Simex's last when used on the road? Is it true they are remoulds? Quote Link to comment Share on other sites More sharing options...
darthdicky Posted March 31, 2007 Share Posted March 31, 2007 As others have said, borrow a GPS - any type (TomTom through to handheld Etrex type ones) will tell you your speed. I find mine is a bit out, at an indicated 60 it's doing 57 really. Thats on 32" 265/75's, and I'm guessing a 100 speedo drive gear. Richard Quote Link to comment Share on other sites More sharing options...
western Posted March 31, 2007 Share Posted March 31, 2007 speedo drive gears Quote Link to comment Share on other sites More sharing options...
Holyzeus Posted April 1, 2007 Author Share Posted April 1, 2007 As an update something must have been changed on my motor cos i did a 170 mile round trip today to do some playing and the speedo is not far off Quote Link to comment Share on other sites More sharing options...
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