mph / engine revs

[Nick]

Can anyone please tell me the road speed per engine revs in top gear of a 1998 1.6K ss with the five speed gearbox, Caterham LSD and running on 13" AO32Rs?

 

My speedo died and the new one seems even more inaccurate, according to my Sigma. I keep forgetting to measure speed over a measured mile, and I haven't got a GPS thingy!

 

Thanks.

Nick

 

Edited by - Nick on 18 Dec 2000 12:33:28

[Mike Bees]

185x60/13 presumably?

 

In 4th gear (not top):

 

3.62 diff: 17.9mph/1krpm

3.92 diff: 16.5mph/1krpm

 

This is assuming that a 185x60 A032R is exactly that - tyres often aren't exactly the size they are quoted at.

 

Mike

[Nick]

Thanks Mike. Yup, 185 x 60/13.

 

What are the two diffs? And how do I know which I have?! I specced my 7 with the AP LSD, but can't see any reference in the paperwork to its ratio.

I take it you use 4th gear as it's 1:1?

And... do you know the maths for working it out?

 

Ask a simple question, get a simple answer, stir for 5 minutes... wink.gif

 

Edited by - Nick on 18 Dec 2000 13:37:49

[Mike Bees]

The AP LSD is independent of the diff ratio, so you could have either. I suspect you'll have a 3.92 since the 3.62 was mostly fitted to Superlights (6-speed 'box with 1:1 top).

 

> I take it you use 4th gear as it's 1:1?

 

Yes. Easy enough to scale it for 5th if you know what the ratio is (0.87 perhaps?).

 

> And... do you know the maths for working it out?

 

I put a spreadsheet together for it. The maths isn't rocket science - you can calculate the tyre diameter given that you know the wheel diameter and the sidewall height (sidewall being 60% of 185, not forgetting that there are 2 sidewalls making up the diameter). From that you can calculate the circumference etc.

 

I'll email you the spreadsheet if you like.

 

Cheers,

 

Mike

[Nick]

Thanks again Mike. 3.92 gives a more likely result.

5th at 0.87 sounds familiar but I'll check.

I have the actual tyre diameter somewhere as I measured it for my Sigma - I took 10 revolutions and divided by 10 to reduce the error margin.

OK, send me a speadsheet over please - it will give me a break from trying to work out NI contributions! sad.gif mad.gif thumbsdown.gif

 

Nick