More on Gear Ratios

[jonhill]

I'm looking at either an SPC or Road and Race Transmission close ratio box to replace the type 9 5 spd I have. This will be the conversion which leaves 4th as 1:1 and shortens 5th to 0.87.

 

My question is regarding 3rd, which is changed from 1.26 on the standard box to a very slightly longer 1.21. I'm worried that this leaves virtually the same gap between 3rd and 4th as before. Since on of my current dissatisfiers is the gap between 3rd and 4th, I'm concerned that I won't find the improvement I'm looking for.

 

Does anybody with these ratios still find a problem with the 3rd/4th gap? Maybe the difference between 1.26 and 1.21 is bigger than I appreciate.

 

I've a K 1.8SS, with a 3.92 diff., currently on 185/60R14 021Rs

 

 

Thanks,

 

Jon

[Peter Carmichael]

The numbers give you a very similar stack of ratios to the six speeder with a 3.62 diff.

 

Your 3rd-4th-5th will be close to the six speeders 4th-5th-6th.

 

Although 1.21 doesn't look much different to 1.26, if you look at the the change in ratio across a change you can get an idea of what revs it will pick up at afterwards.

 

i.e.

 

3rd to 4th 1/1.21 = 0.8264 (revs drop to 82.6% of change up revs)

 

compare this to

 

1/1.26 = 0.794 (revs drop to 79.4% of change up revs)

 

If you change up at 7200, this will be the difference between pickup at 5950 rpm as compared to 5717 rpm. (233 rpm extra). The six speeder would give you 6164 rpm (another 214 rpm extra).

 

[CHRIS CLARK]

Peter.

 

Like your explanation in % terms. Have you got same for the std. 5 sp (XR4I) box? Ta

[jonhill]

Chris,

 

Here are the ratios for the standard box, and also the CR box. You can do the % calculations from Peter's example:

 

STD RRT/SPC

 

1 3.36 2.39 (2.04, 2.2 are options)

2 1.81 1.54 (1.69)

3 1.26 1.21

4 1 1

5 0.82 0.87 (0.93)

 

I have to say 233 rpm doesn't sound like a big difference, though the comparison with the 6 speeder looks good.

 

We've heard rave reviews from the VX contingent, has anyone with a K series changed to these ratios, and can give a

qualitative before and after comparison?

 

 

Cheers,

 

Jon

[EFA]

On an engine which can rev to 8500rpm the six speeder and a 3.38:1 diff are a great set of ratio's with 22" ACB10's on the rear

 

61 in first

82 in second

103 in third and so on to 6th which gives 4800rpm cruising at a ton.

 

If you buy a 5spd Quaife make sure

 

1. You get the Heavy Duty version with needle roller internal bearings.

2. Steel synchro's are a waste of time

3. The 5th gear retainer is the deep seat version (stops 5th fallling off the shaft!)

4. Use a quick shif and this gives the 5 spd a better shift than an escort sport 4 spd. (Both are MUCH better than the 6 spd which guarantees a miss every 3rd attempt of getting second form fourth!)

 

Arnie

 

 

 

[jonhill]

I believe Road and Race Transmission's boxes have quaife internals.

 

Arnie wrote:

"If you buy a 5spd Quaife make sure

 

1. You get the Heavy Duty version with needle roller internal bearings."

 

I was thinking of the clubmans box, which is £230 less than the heavy duty box you describe. Phil at Road and Race Transmissions said this was more than up to the job of my 140 bhp K. Do you disagree?

 

"2. Steel synchro's are a waste of time"

 

What are the alternatives? I wasn't offered any choice on this, what should I be asking for, and why?

 

"3. The 5th gear retainer is the deep seat version (stops 5th fallling off the shaft!)"

 

Sounds worrying. Are you saying not all boxes are put together in such a way as not to fail like this?

 

"4. Use a quick shif and this gives the 5 spd a better shift than an escort sport 4 spd. (Both are MUCH better than the 6 spd which guarantees a miss every 3rd attempt of getting second form fourth!)"

 

How does this differ from the standard shift? Again it wasn't brought up in my conversation with Phil.

 

Thanks,

 

Jon

[Chelspeed]

The clubmans box is reputed good for about 180bhp and 8000rpm. I ran one with 250 bhp and 9000rpm for a year before upgrading and it survived OK. Yours will be fine.

 

Steel baulk rings are an option offered by some Quaife dealers for people who have trouble with wearing out the synchros with the std brass ones. I never had any problem with the std brass baulk rings. You wouldn't be offered steel ones unless you go to the few Quaife dealers who offer them, you won't need them I wouldn't think. If you find you trash synchros then consider it for next year.

 

Some users swear blind by them, others don't. Normal YMMV stuff.

[Alex Wong1697456877]

I went for the standard synchro rings against the advice of Chairman Roger who has destroyed a few of these in the past with his 250BHP Vx. I think he's had much less trouble since changing to the steel ones but the gearchange is nowhere near as nice. I think Jane farthing's Vx has done the same as well.

 

The steel rings give a sort of crunchy shift and it needs a very firm positive shift to go from gear to gear cleanly. I'll be kicking myself when my brass ones let go though.

 

 

 

Alex Wong

www.alexwong.net

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Edited by - Alex Wong on 16 Oct 2000 00:13:12

 

Edited by - Alex Wong on 16 Oct 2000 00:14:35