6 speed v 5 speed

[Bobo W]

A friend is in the process of buying his first Caterham and I'm giving him pointers on the various options and the types of spec that he should be looking for.

 

From reading BC it would appear that the 6 speed box is more desirable over the 5 speed especially for K-series engined cars. However I'm not sure why. I guess if you're doing lots of track work a 6 speed will let you get more from the car but if the majority of miles are on the road, does it still make that much difference ?

 

Coming from someone who drives an HPC where the torque makes the number of gears largely irrelevant, choice of gearbox is not something I considered in my purchase but at the same time I'd like to be able to give him a level view on the issue so that he doesn't then discount really good cars just because they don't have the 6-speed box.

 

Thanks

[Stationary M25 Traveller]

6-speed has the edge for track use. I find the 5-speed great for road use (1.8k-series VVC). The 6-speed is a lot higher revving for any given speed .... the 6th gear is the same as my 4th gear, so engine revs a bit tiresome for any long journeys at speed.

 

 

[Nick Pargiter]

The 6-speed box was (I think) developed mainly to go with the 1.4 K-series as this didn't have that much torque. So it depends which engine your friend is looking at as to whether it is best to choose a 5-speed or 6-speed. It also depends on your style of driving and what you intend to do with the car.

 

My car was originally a 1.4ss and the 6-speed worked really well as it kept the engine revving where it should be, at the top 😬

[jingars]

I have a 1.8K that was originally a 1.4. It has a 6 speed box.

 

I echo SM25T's and Nick's comments; great for a thrash but a wee bit of a pain on motorway cruises.

 

You are right to look at the overall package of any prospective purchase; don't get hung up on the number of cogs.

[u01rsb]

Maybe a six speed would also be better then if you could change the diff ratio, giving you a compromise on more gears to keep it in the higher torque band but also not so much of a pain on motorway miles.

 

I love my 6 speed sequential in my busa but would probably find any journey off the track a pain in the 🙆🏻

[Bobo W]

Currently looking at a 1.6K upgraded to Supersport with 5 speed. It looks really nice, top spec and all that, bit overpriced in my mind but still a good buy.

[Alex Wong1697456877]

Have had :

 

standard type 9 5 speed

Quaife/SPC Semi Helical and straight cut close ratio type 9's

Extreme close ratio 5 speed Elite sequential (was actually Dave Kimberly's sprint car box)

Not quite so close ratio 5 speed Elite Sequential

Caterham 6 speed

 

All with Vx's engines from 200 to 250BHP.

 

The standard 5 speed is really all wrong even for a Vx. 1st too short, gap from 2nd to 3rd too big, 5th too tall. The SPC box was a massive improvment.

 

Elite boxes just too unpredictable but when they were working, they were brilliant on track and tolerable on the road.

 

6 speed with diff ratio change to suit has been very good.

 

For a road Seven I would choose between a close ratio 5 speed or 6 speed. If it's standard 5 speed or 6 speed, it's a no brainer to go for the 6 speed with appropriate diff ratio. The ratio's in a standard 5 speed really dont suit the Seven with any engine.

 

I went for 6 speed in the end because of concerns with 5 speed synchro weakness, but that's really only an issue for cars used alot on track.

 

For a K series car, the 6 speed is preferable to 5 speed close ratio because of the lack of torque. 3.62 diff probably best for a road car maybe?

 

For a torquey Vx, 6 speed is still good, but you do need to change to diff ratio. Mine is a 3.38 which I think suits the engine and box very well.

 

If you go for a close ratio 5 speed, 3.92 diff seems to work well with a Vx for a road car.

 

have never driven a Duratec but I get the impression they're like a lightweight Vx in there character?

 

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Edited by - Alex Wong on 24 Apr 2009 12:06:55

[Bricol]

It's a fun car - and the 6spd adds to the fun.

 

I have a 1600K, with 6 spd and the 3.92 diff - fantastic! Yep, high revs at motorway speeds, but so what? How many motorway miles are intended as a Caterham isn't exactly a motorway car anyway. Having said that, I've done quite a few charging down the mainland to reach more sunny weather the other side of the Alps - with an autocom and musac, it's fine.

 

When I bought mine, I drive the 6spd demonstrator at Caterham and then asked for a run in a similar engined 5spd . . . had decided on the extra cash within 100yds . . .

 

Bri

[Windy Corner]

I remember having this debate before I bought mine (can't seem to find the thread though ☹️)

 

The conclusion I came to then, as others have said, 5 speed for road (taller 5th), 6 speed for track (closer ratios). As it turned out the car I went for had a 5 speed box, so I was happy, as I was looking for road with the odd track day

 

With the benefit of hindsight, a couple of things I have noticed, is that when approaching a corner and changing down, 3rd is too high (car chugs around corner) and 2nd seems too low, which seems to back up what Alex said above, gap between 2nd and 3rd is too large.

 

The lower 5th for cruising is a good idea, but what the difference in noise level between (70mph in 5th in 5 speed) 3452 rpm and (70mph in 6th in 6 speed) 4210 rpm is debatable. I have also found that I tend to avoid motorways anyway so tend not to cruise for long periods in top gear, deliberatley tend to find the A roads, with roundabouts where a 6 speed box would be nice. (I used Gearcalc.exe for the above using 195x45x15 tyres)

 

Next time round 🤔, I would seriously consider the 6 speed instead................but then I am perhaps biased as all my diesel tintops have 6 sp gearboxes 😬

 

Hope that this is helpful

 

Rik

 

Roadsport SV 1.6 Sigma 150

in Viper Blue here

[Graham King]

These are just my thoughts but I have had a 1.8K with a 5-Speed and my current 1.8 Superlight with a 6-Speed, in my opinion the 6-Speed box is by far the better box to live with on a day to day basis.

 

The change is much better and the ratios much more suited to the car, in particular 1st on the 5-Speed (although the likes of BGH can change this for you). I take the point regarding motorway miles and if you were going to regularly do lots of motorway driving then the 5-Speed may be better but for most people most of the time I think the 6-Speed is better.

 

Anyway as I said just MHO and others will disagree but in a K-Series I think the 6-Speed completes the car.

 

Graham.

 

R7 GPK

Superlight #85

[Bobo W]

Thanks for the feedback.

[Windy Corner]

Ah Found the link to my thread, the gearbox discussions are about midway down page 2

 

here

 

Also my gearcalc figures were a bit out, as I had forgotten to change the ratio of the diff

 

70mph in 5th in 5 speed) 3452 rpm and (70mph in 6th in 6 speed) 3888 rpm 😳 but please check them yourself..........

 

Rik

 

Roadsport SV 1.6 Sigma 150

in Viper Blue here

[john milner]

I got a 5 speed VVC and like it but I think it all depends on how the car is going to be used.

For example my 4th is the same as a 6 speeds 6th. I would not want to cruise up a motorway in 4th whereas my 5th is perfect.

[Geoff Wilcx]

Over the winter I upgraded my K to 6 Speed - no looking back - with the standard diff it was high revs on A Roads but now also upgraded the diff 3.62LSD and I have to say its perfect - once you've driven a 6 speeder then there is no going back

 

My Winter '08 Upgrade was to a screaming DVA K05.

 

www.geoffwilcoxphotography.co.uk

[Richyd]

I did exactly the same as Geoff with my 1.6ss DVA'd K05 - 6 speed with modified diff is the way to go - you will never find yourself in the wrong gear, and the 6th ratio is fine on long journeys (I did 2500 miles in 4 days in mine). In a SS the 5-speed box is a pig, the ratios are too wide IMHO. It's probably fine however in a more tourq'ey engine...

 

Now sold...C7 DVA - It's a 1.6 187bhp screamer :-(

[Roadsport06]

I have the 5 speed. On building from new I had 2 options (financial): 1.6 6speed or 1.8 5speed. I opted for the 5speed, I think its fine for road use, the extra torque is better with the 5speed. I hired a 1.6k with 5 speed and it never quite had the feeling of being in the right gear as the torque wasn't there. I would hate the thought of my 4th gear being my top gear on the road though. If the engine needs to come out at some point , I will certainly give SPC a call to ask about the cost of fitting a longer 1st gear. This is a regret on building the car.

 

BRG and Yellow nose now with added brooklands