barf 0 Report post Posted October 25, 2007 just wondering what size tyre I should be using on 323i e30 5-speed? the speedometer is incredibly inaccurate, indicating about 10-20kms faster than actual speed. I'm using the factory mag-alloy rims with 65profile rear 60 front thanks Quote Share this post Link to post Share on other sites
jpp 0 Report post Posted October 25, 2007 just wondering what size tyre I should be using on 323i e30 5-speed? the speedometer is incredibly inaccurate, indicating about 10-20kms faster than actual speed. I'm using the factory mag-alloy rims with 65profile rear 60 front thanks What year car, and what instrument cluster do you have? I'm not sure, but maybe that needs addressing? Quote Share this post Link to post Share on other sites
Andrew 30 Report post Posted October 25, 2007 Which factor mag alloy wheel? And 10-15 k wrong at 100kph isn't that bad for an E30 Quote Share this post Link to post Share on other sites
ducatiss 1 Report post Posted October 25, 2007 The wrong instrument cluster or at least VDO meters in a motormeter cluster can cause this issue. 10 - 15 percent is way too much imo even for an e30. Quote Share this post Link to post Share on other sites
barf 0 Report post Posted October 25, 2007 sorry for not including more detail, it's 100% unmodified apart from me replacing ignition coil, leads, spark plugs, fuel pump and fixing the fuel injection computer, electric windows and miscellaneous. as far as I know the instrument cluster is original. - year is 1985 - wheel rim is 14" it has 'e35' marked on it. does that identify the wheel as being from a newer car? Quote Share this post Link to post Share on other sites
ducatiss 1 Report post Posted October 25, 2007 re the wheels being marked e35 - no I dont think that e35 means they are off a later car (other members may correct me there though). I would try another complete cluster - maybe another member has one they could lend you to try or something. Was it reading correctly before you started on all your repairs?? Quote Share this post Link to post Share on other sites
bravo 35 Report post Posted October 26, 2007 Reading 10kms fast is standard for an e30. Every one I have owned has been. What is your tyre size. We have your rim diameter and you profile, but still need to know the width as profile is a percentage of width, not a number of mm. Factory standard is 195/65/r14 Speedo sensor is on the diff, so only rear wheels count for speedo reading. for your 65 profile tyre, widths of 195 or 205 are OK. Bigger than 205 will creat 5% or more SLOWER reading. 185 or below will create 5% or more FASTER reading. I doubt you have 185 or narrower! Quote Share this post Link to post Share on other sites
gmccormack 0 Report post Posted October 26, 2007 What makes you think the speedo is out??? With the engine sitting dead on 2000rpm in forth gear what speed is it indicating?? 4.11 diff @2000rpm = 56km/h 3.64 diff @2000rpm = 63km/h 3.46 diff @2000rpm = 66km/h 3.45 diff @2000rpm = 67km/h Quote Share this post Link to post Share on other sites
Silver Fox 43 Report post Posted October 26, 2007 That means 168 kph just past the kink on the back straight in my 318 at puke? Quote Share this post Link to post Share on other sites
gmccormack 0 Report post Posted October 26, 2007 That means 168 kph just past the kink on the back straight in my 318 at puke? Yes, assuming 195/65/r14 tyres and a 4.11 diff, you will hit 167.65839km/h at the a 6000rpm rev limit. Quote Share this post Link to post Share on other sites
Silver Fox 43 Report post Posted October 26, 2007 How about 205/50/15's then? Quote Share this post Link to post Share on other sites
gmccormack 0 Report post Posted October 26, 2007 How about 205/50/15's then?I don't have a 205/50/15 in my garage, can you measure one of yours. Post the diameter on the thread and i'll calculate the new speed. Quote Share this post Link to post Share on other sites
bravo 35 Report post Posted October 27, 2007 195/65/14 is 609mm diameter 205/50/15 is 586mm diameter so you'd be going 3.8% slower. Quote Share this post Link to post Share on other sites
barf 0 Report post Posted October 27, 2007 thanks for all the replies tyre is 195/65/r14 the speedo is about 10kph fast at 50kph and 110-115 faster at 100kph actual 10kph faster sounds about right! i'll get a tape measure out while i'm asking the head makes an awful tapping noise, what is this usually or likely to be? Quote Share this post Link to post Share on other sites
bravo 35 Report post Posted October 27, 2007 Tapping noise is the tapets. They can be adjusted. Sometimes on older motors even after adjustment to correct spec, they are still noisey. Its an e30 trait. Quote Share this post Link to post Share on other sites
gmccormack 0 Report post Posted October 27, 2007 195/65/14 is 609mm diameter 205/50/15 is 586mm diameter so you'd be going 3.8% slower. I get 167.49196km/h @6000rpm for a 609mm diameter tyre and 161.16788km/h @6000rpm for a 586mm diameter tyre, if both are using a 4.11 diff. Quote Share this post Link to post Share on other sites
M325is 0 Report post Posted October 27, 2007 Hahaha E30s crack me up, they have so much character. Its great, when your partner drives they dont speed!! Quote Share this post Link to post Share on other sites
bravo 35 Report post Posted October 27, 2007 (edited) I get 167.49196km/h @6000rpm for a 609mm diameter tyre and 161.16788km/h @6000rpm for a 586mm diameter tyre, if both are using a 4.11 diff.Which equates to 3.77575% I bow down to your greater precision and 5 decimal places lol. Edited October 27, 2007 by bravo Quote Share this post Link to post Share on other sites
hotwire 352 Report post Posted October 27, 2007 I get 167.49196km/h @6000rpm for a 609mm diameter tyre and 161.16788km/h @6000rpm for a 586mm diameter tyre, if both are using a 4.11 diff. David, If you want to go faster down the back straight in the 318 then cheat & put 14" wheels on with original 195/65s Quote Share this post Link to post Share on other sites
