Evening all. Managed to find myself a Capri laser atlas axle today but it has the 3.75 crown and pinion fitted. What would be the best ratio replacement for a good 70mph cruising speed without silly rpm and still retaining good acceleration. Engine is a 2004 gsxr1000. Many thanks

there isn't really a good ratio for 70mph cruising in a BEC with a live axle.

Anything has got to be better than my 6k at 50mph!!! My ears bleed.

did one of the capri's not have a 3.08:1 axle. that could be slightly too much for the 1000cc motor though? the busas can run a 3.14:1 diff i think.

This any interest http://www.locostbuilders.co.uk/forum/23/viewthread.php?tid=121319

You might well get away with the aforementioned 3.08 ratio IF you have 13" wheels and suitable tyres.
Perhaps someone will post a link to the gear ratio-final drive ratio-wheel size-speeds in gears calculator........?

isn't there a 3.44 (yep on ebay)wouldn't that be better, I was running a 3.89 in my english axle and changed to 3.54 and that made my blade 919 better but still a bit wearing.

cheers Pete

Yeh believe the 2.8 Capri axle was a 3.08. That's what I Was thinking at first but if a busa lump turns the 3.14 then maybe I should go for the 3.52. The chart is great by the way thanks for the link will look in detail when a little more awake tomorrow

Got your post the second after I returned mine. Looking now. Gotta love eBay. Thanks

yours may still be ok with 13" rims and the 3.08 axle if it has the grunt to rev out in top gear. what are the torque figures on the gsxr like compared to the busa?

I'll be interested in hearing what you have to say if you change.

I imagine it will still be pretty annoying sitting at a constant speed in a BEC... I avoid main roads/motorways at all costs as it does my head in so much. I looked at the speed calculator a year or two ago and assumed the two english axle ratios were the only ones available without going bespoke... my bad.

Don't compare between bike for your ratios, as their internal ratios differ a bit

For example. My old RF900 did 6K rpm at 70mph on a 3.92 diff.
Which is simular to my now ZX12r running a 3.62 diff.
Running 17" 225/45 on the rear which helps.

Fast tourers are more likely to have lower ratois.

Right got myself an atlas with a 3.44 diff gonna give that a go. Now where is the best place to get the brackets to fit my trailing arms ( 4 of em) I'm fine welding them on just need to know best place to buy them if you can. Thanks sam

What like these?
Locost / Kit Car Escort MK II Axle Brackets | eBay UK

I will be very interested how you get on as i need more top speed.
Tony

[Edited on 14/4/11 by tony.g]