Gear ratios

[Rob]

I have a 1.4SS and I feel it would benefit hugely from closer gear ratios. My options appear to be:

 

- Change the diff ratio

- Fit a close ratio 5 speed

- Fit a close ratio 6 speed (expensive)

 

I know this would remove the "over-drive" that the current 5th gear gives me, but it is so long I hardly ever use it anyway, and on the track I never use it.

 

Anyone have any advice??

 

Rob

 

[Mike Bees]

6-speed box is perfect (ratios-wise) for the 1.4KSS.

 

Before I bought my first 7 I went to the Caterham showroom test-drove two 1.4KSS's, one with a 5-speed and one with a 6-speed. That convinced me that whatever the cost was the 6-speed was the way to go, it felt like a different car (OK if you want to be pedantic it *was* a different car smile.gif).

 

Mike

[Dartmoor7]

I would love to do the same with my 1.4 SS, on the road I find it a 3 speed 'box.

Option one is no good because 1st gear will become useless.

If you can afford it get the 6 speed.

If not get a close ratio 5 speed where 1st is higher and all the other gears lower.

[Peter Carmichael]

Changing diff ratio does not make the gearing closer.

 

The rev drop between gears will remain the same. The only way this has any effect is if you make 1st unusably low and bring fifth gear down so that you can top out the revs in fifth. This will mean that you are a gear higher all the time and all gearboxes are designed with the higher gears closer stacked than the lower ones (apart from stratospheric overdriven fifth gears).

 

A new gearset for the five-speeder is possibly the most economical route, as suggested. Quaife? BGH? SPC? All these guys seem to know what they are up to. You could also talk to Phil Stewart at Road and Race Transmissions for advice (he rebuilds all the Caterham race series gearboxes).

[Petrolhead]

Out of interest how much is a Cat 6 speed box?

 

 

[Peter Carmichael]

I think it was in the region of £3000 +VAT, remembered from the Caterham parts CD-ROM.

 

It was close enough in price to the new Quaife six-speed sequential boxes to make them look like good value. It is a shame that I have not yet heard a good opinion of the Quaife sequential boxes, but I guess what I have heard may have been influenced by similar reasoning to Keith's preference for the R500 over the Blackbird.

 

A synchromesh H-gate box is going to be better on the road than a dog sequential box. I also suspect that minimising drivetrain inertia would be the key in getting the sequential shift to work properly (clutchless upshifts), following the technical lead from the biking fraternity.

 

Now, who do I know who has a very low inertia k-series drivetrain and a penchant for track drivingquestion.gif

 

Edited by - Peter Carmichael on 13 Sep 2000 14:05:55

[Mike Bees]

2,291ukp inc VAT on the CD-ROM, although some prices have gone up since it was published almost a year ago.

 

Mike

[Alex Wong1697456877]

I was never convinced about the 6-speed box till I tried one in a 1600SS. It is as perfect match for the engine as I can imagine. Worth the extra for the smaller K-series cars, I think.

[SLR No.77]

Rob,

 

For a close ratio 5 speed, check out http://www.spcomponents.co.uk

 

This is a complete box (outright) for approx £1000 + VAT. Well recommended as I understand.

 

Stu.

 

[Alex Wong1697456877]

I use one of the SPC boxes and it's brilliant for the Vx engine. I imagine it would be a good match for the Ford, and even with the K, it would be a vast improvement on a standard type 9. It's still not nearly as close geared as the 6 speed though which really does go with the revvy nature of the k engine.

 

Alex

[Graham Perry]

Does anyone know if any manufacturer does a 5 speed type 9 ford gearbox where 5th is 1:1 rather than an overdrive (typically 0.87:1)

 

The beauty of the Caterham 6 speed is that it has no overdrive top so pulls in all gears. A five speed equivelant would be nearly as good, and would have the effect of lowering 4th, which is the gear where most Caterhams stop pulling hard due to the poor aerodynamics. Obviously this partly depends on your diff ratio, but fifth has always felt to high on mine even with a 4.44 diff.

[Mike Bees]

I thought Quaife did? I also thought that the info was on their website but I can't find it there now.

 

Mike

[elie boone]

quaife web site:www.quaife.co.uk

 

 

[Mike Bees]

Yes... but where does it list the ratios available for Ford 'boxes?

 

Mike

[Gary Drew]

Quaife don't list their ratios .... but I know a site that does:

http://www.motorsportparts.co.uk/quaife.htm

[Nick]

There is a DOS based car acceleration programme at

http://www.home.earthlink.net/~patglenn/ct.html. If you want it, download the DOS version from the bottom of the page, not the Windows one at the top.

 

It is pretty comprehensive and whilst only a guide, does seem reasonably accurate when compared with Santa Pod runs. Whilst figures may not be accurate (the 0-60 time for my 7 seems optimistic!) you may find it useful for comparing gear ratios - as per the figures below.

 

The 0-60 times show my standard box just as good as the 6 speed - but the 30-50 and 50-70 times tell a different story. I have included the R500 for a bit of a larf! Interestingly though, when I was at Combe earlier in the year, a friend was having to be careful in his R500 because of the noise boys, yet he seemed just as fast pottering in 5th as I was caning mine in 3rd - these figures seem to bear that out.

Selected Cars: 1. 7 - MY 1.6K SS

2. 7 - MINE WITH 6 SPEED BOX

3. 7 - MINE WITH SPC BOX

4. 7 - R500

-------------------------------------------------------

Car Number 1 2 3 4

--------- --------- --------- ---------

Time to Speed

0-30 mph.... 1.6 1.9 2.0 1.4

0-40 mph.... 2.9 2.6 2.8 1.9

0-50 mph.... 3.9 4.0 3.6 2.3

0-60 mph.... 5.0 5.1 5.4 3.5

0-70 mph.... 7.1 7.1 6.7 4.3

0-80 mph.... 8.9 9.4 9.2 5.7

0-90 mph.... 11.0 11.6 11.4 6.6

0-100 mph.... 15.4 15.6 15.9 8.4

 

-------------------------------------------------------

 

Time to Distance

0-100 ft..... 2.8 2.9 3.0 2.5

0-500 ft..... 7.5 7.6 7.6 6.4

0-1320ft..... 13.9 14.1 14.0 11.8

@ mph .... 95.9 95.7 98.3 117.9

 

Top Speed.... 119 119 118 152

 

-------------------------------------------------------

 

5-60 mph, 1st

Gear Start... 4.8 5.1 5.6 3.4

 

-------------------------------------------------------

 

30-50 mph

2nd Gear..... 2.0 1.7 2.3 1.2

3rd Gear..... 3.1 2.3 3.2 1.5

4th Gear..... 4.2 2.9 4.2 1.9

5th Gear..... 5.8 3.5 5.2 2.3

6th Gear..... 4.2 2.8

 

-------------------------------------------------------

 

50-70 mph

2nd Gear..... 2.5 1.2

3rd Gear..... 3.1 2.4 3.3 1.5

4th Gear..... 4.4 2.9 4.4 1.9

5th Gear..... 6.0 3.6 5.5 2.3

6th Gear..... 4.4 2.7

 

Edited by - Nick on 14 Sep 2000 13:34:18

[Rob]

Thanks for the advice everyone. It looks like I have 2 realistic options:

 

- fit a close ratio 5 speed

- save up for a new 6 speed car (I reckon it's uneconomic to spend 3000 on my existing car).

 

Where's my piggy bank......

[Alex Wong1697456877]

I'd go for the close ratio 5 speed. I managed to get a 2nd hand newly rebuilt straight cut 5 quaiffe 5 speed for 350 quid but I traded it in for the SPC box. At that price, you could get a different diff ratio (4.44?) and it should be a pretty good setup I think. Obviously no experience of this but it should be.

 

It makes the car harder to sell though (non standard bits always do) so if you are thinking of getting a new car, I'd go down that route. You could always find a 1.6 engine later though. I'm so attached to my car that I'll probably never sell it although I predict that by 10 years time, it will probably have had every bit changed at least once!

 

Steve at SPC might still have the box I part exchanged.

 

 

 

Alex Wong

alex.wong@lotus7club.co.uk

www.alexwong.net

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Edited by - Alex Wong on 15 Sep 2000 01:40:56

[CHRIS CLARK]

Well guys, they Kent 7 club had a factory tour at "Quaife" last night & mighty impressive it was too!

 

Right, here goes; 5 speed synchro box with top 1:1 =2895 UKP

or; gear kit

1st=2.04

2nd=1.540

3rd=1.210

4th=1.1

5th=0.930

 

560 UKP plus vat of course.

Call 01732-741 or info@quaife.co.uk

[Gary Drew]

Would that it were that simple Chris,

 

The ratios you quote (ie. 2.04 first gear) are for the 'race' ratios. That gives you a very tall first gear for road use.

 

If you plan road use then the 'rally' ratio set (ie. 2.39 first) is the better choice.

 

And of course it all depends on optimising with your diff ratio and rev range ..... and so it goes on.

 

Whatever, Quaife, Tran-X or SPC are all well-proven suppliers and will help you choose the correct set-up.

 

[Graham Perry]

Further to my earlier note, I understand that the new sequential box made by quaife in both 5 and 6 speed has a 1:1 top gear. I wonder why they don't offer this ratio for the type 9 in their catalogue, when their new sequential box is basically a type 9 anyway.

Does anyone know what intermediate ratios the 5 and 6 speed sequential boxes use, as my catalogue doesn't list any ?

[Alex Wong1697456877]

4th in a type 9 is always 1:1 as it just mates the in and output shafts. This, as far as I know is not changeable.

 

Alex

[Mike Bees]

I'm *sure* that Quaife do a 5-speed 'box using a Type 9 casing that offers a 1:1 5th gear. And a 6-speed too. The sequential option is just that, an option at extra cost.

 

Mike

[Graham Perry]

Thats exactly what I thought. I suspect they may only be on sale with the sequential option until demand for that dies down. I will contact them later in the year.

[Chelspeed]

> Does anyone know what intermediate ratios the 5 and 6 speed > sequential boxes use, as my catalogue doesn't list any ?

 

4 speed is:

2.04, 1.54, 1.22, 1.00

 

5 speed with overdrive 5th is:

2.04, 1.54, 1.22, 1.00, 0.87

 

5 speed with direct top is:

2.39, 1.69, 1.34, 1.15, 1.00

 

6 speed with overdrive 6th is:

2.39, 1.69, 1.34, 1.15, 1.00, 0.87

 

Sorry didn't make a note of the other option, 6 speed with 1.00 top.