Close ratio gear set

trident sam · Dec 1, 2014

Is there any real advantage to fitting a close ratio gear set to a standardish Mk.3 850, bike runs good but as the gears aren't that expensive what do you guys think.
sam

johnm · Dec 1, 2014

What do you want to do with the bike ?

If its for the road in the city then absolutely no. Without changing the final drive sprockets (to lower the overall gearing) the first gear on the CR sets is so high that riding in traffic or on normal roads is pure misery. If you live way out in the country and never have to drop below 45 mph then ok. (I see your in Liverpool and the way I remember that traffic Id say a definite no)

We gave up on CR gearing for our kind of short circuit clubmans racing because by the time you got the bike moving all the rest of the bikes were at the first corner.

If your racing at the Isle of Man then thats a different story.

olChris · Dec 1, 2014

trident sam said:
Is there any real advantage to fitting a close ratio gear set to a standardish Mk.3 850, bike runs good but as the gears aren't that expensive what do you guys think.
sam

Ditto..... "what do you want from the Mk3".. If your like me and hate that first gear ratio around town and had the $$$$$$$$ and research time, a 5 or 6 speed g/box would solve some many problems... eg, easy off at the lights and more speed at 5k rpm in top..... Not saying that you will ever want to go faster than the speed limit or have the ability to piss off other newer bikes at the traffic lights... mmmmh no cant be done on an old Norton.. :lol: :lol: :lol:

acotrel · Dec 1, 2014

I used a 4 speed CR box in a few races and won a couple when there was nobody of any importance there. When it came to the fast stuff I only got one good start and that only by cooking the clutch. I was up beside the lead bike when I popped a fuel line and stopped. It was all too hard, and I can understand how main shafts get bent. I've fitted the 6 speed TTI box however still haven't used it. If you are intent on beating someone who is also on a commando the 4 speed CR box is superior to the wide ratio - however still pretty useless. For racing the standard box is appalling. The close box fitted with a standard ratio first gear might be OK. - Big gap between first and second gear. Just getting the bike moving from a stand-still is the major problem. On most race circuits you don't go below second gear once you are moving, and It should be OK on the road.

Matchless · Dec 1, 2014

Sam,

As others have said, it all depends on how you use the bike. I have the RGM C.R. gear set in my 750. For thrashing around on open roads with lots of corners it's miles better than standard. It gives the engine a much easier time when changing down for a corner. The downside is first gear is (I think but I would need to check) about 2.05:1 as opposed to 2.56:1, making town work slightly more of a pain.
If you REALLY love your Commando, sell your soul / children / wife & buy a TTI 5 speed.

Martyn.

acotrel · Dec 1, 2014

When I bought the TTI 6 speed box, I didn't really think about what I was doing. With the 4 speed CR box it is only first gear which is a problem. Once the bike is rolling the box is perfect everywhere. However you find that when the top three gears are close, you can raise the overall gearing. That makes the problem of the high first gear worse. I didn't realise that I had about four sets of gears from various old Nortons, and the first gears in them are all different ratios and all fit the AMC type box. These days all races are clutch starts - with the old push start the high first gear was not a problem. With that high first gear my 850 tended to stagger off the start in a race, unless you really gave it heaps - not a good thing to be doing. With a standard commando ratio first gear in the 4 speed CR box the bike would be a lot of fun on public roads - you will probably lose your licence for speeding.
With my bike, gearing has been the main stumbling block in getting it to go fast. It is very deceptive. Good gearing behind an almost standard motor can make for a very fast bike. For road use, you don't need more than four speeds in the gearbox with a commando motor.

SteveA · Dec 1, 2014

Matchless said:
Sam,

As others have said, it all depends on how you use the bike. I have the RGM C.R. gear set in my 750. For thrashing around on open roads with lots of corners it's miles better than standard. It gives the engine a much easier time when changing down for a corner. The downside is first gear is (I think but I would need to check) about 2.05:1 as opposed to 2.56:1, making town work slightly more of a pain.
If you REALLY love your Commando, sell your soul / children / wife & buy a TTI 5 speed.

Martyn.

If you really love your road Commando, build a nice standard box......or maybe get a Quaife, which still looks pretty original

If you want to race your Commando, or seriously abuse it (which you wouldn't do if you loved it would you ;-) ) thats when you need a TTi.....

Jagbruno · Dec 1, 2014

olChris said:
Not saying that you will ever want to go faster than the speed limit or have the ability to piss off other newer bikes at the traffic lights... mmmmh no cant be done on an old Norton.. :lol: :lol: :lol:

Naaaaaaah...can't be done... :mrgreen: :mrgreen: :mrgreen: :mrgreen:

B+Bogus · Dec 1, 2014

I agree that the standard gearing can be a handicap on anything other than town riding, which I avoid anyway.
I have to admit to being tempted myself for a while, and would still consider it as a compromise solution.

I find the gap between 1st and second can be a real pain even with a 21T sprocket, especially on downshifts (MkIIA, so I'm assuming the same as MkIII). The best way to avoid the back end squirming around seems to be to shift into first only when the revs have dropped right down, so the engine braking effect has pretty much gone, and not ideal for 'getting on with it' on my favourite roads

My Combat was great in this respect, but the gap to third felt too big (20T sprocket) - it might be just fine with a 19T, or with a less peaky motor.

I bit the bullet and bought a Quaife 5-speed, but as I haven't got my finger out to finish the bike yet I can't say how good it is. :roll:

Rohan · Dec 1, 2014

B+Bogus said:
The best way to avoid the back end squirming around seems to be to shift into first only when the revs have dropped right down, so the engine braking effect has pretty much gone, and not ideal for 'getting on with it' on my favourite roads
My Combat was great in this respect, but the gap to third felt too big (20T sprocket) - it might be just fine with a 19T, or with a less peaky motor.

Didn't the ratios in the 850 box change, so that the gap to 3rd was less ?

Its perhaps worth pointing out that close ratio boxes aren't overdrive boxes (?), so although the gap between individual gears is less,
1st isn't going to be any lower, and top won't be any taller,
you just have more gears to choose from in the same spread of speeds covered.

L.A.B. · Dec 1, 2014

Rohan said:
so although the gap between individual gears is less, 1st isn't going to be any lower,

That isn't necessarily true, for instance, the Quaife C.R. 4-speed K/S box had a higher 1.99:1 ratio 1st. gear, and the Quaife C/R race box 1st was 1.8:1 compared to the standard 2.55:1 Commando 1st. gear.

Rohan · Dec 1, 2014

L.A.B. said:
That isn't necessarily true,

Having a higher ratio 1st gear CERTAINLY doesn't give a lower 1st ratio !!
Whatever were you thinking of LAB ?

I once had a little trials bike, which incidentally had a huge rear sprocket.
All 5 of its gears would have been lower than a Commando 1st gear. !!
(Flat out in top gear was less than 40 mph.)
But it was easy to pull away in 1st gear, even while climbing vertical trees....

Unless we are having conniptions over lower numerical ratios versus overall gear ratios ?

L.A.B. · Dec 1, 2014

Rohan said:
L.A.B. said:

That isn't necessarily true,

Click to expand...

Having a higher ratio 1st gear CERTAINLY doesn't give a lower 1st ratio !!
Whatever were you thinking of LAB ?

Correct, sorry. I must have read it backwards.

acotrel · Dec 1, 2014

B+Bogus said:
I agree that the standard gearing can be a handicap on anything other than town riding, which I avoid anyway.
I have to admit to being tempted myself for a while, and would still consider it as a compromise solution.

I find the gap between 1st and second can be a real pain even with a 21T sprocket, especially on downshifts (MkIIA, so I'm assuming the same as MkIII). The best way to avoid the back end squirming around seems to be to shift into first only when the revs have dropped right down, so the engine braking effect has pretty much gone, and not ideal for 'getting on with it' on my favourite roads
My Combat was great in this respect, but the gap to third felt too big (20T sprocket) - it might be just fine with a 19T, or with a less peaky motor.

I bit the bullet and bought a Quaife 5-speed, but as I haven't got my finger out to finish the bike yet I can't say how good it is. :roll:

An answer to the very low first gear making down-changes hazardous might be to fit a slipper clutch. Going up through the box once the bike is rolling should not be a big problem. You might lose a bit of acceleration for a few metres off the traffic lights, however once you are changing up through the top three gears with the motor on the boil, the bike should be very fast. The 4 speed CR box with raised overall gearing is excellent once the bike is rolling, then you only use the top 3 gears anyway in racing.

SteveA · Dec 1, 2014

What is it with the low first issue on a road bike.....without meaning to be too impolite....

On a road bike you can learn to ride with the ratios you have! Why do you need to go back to 1st on the move with a tractable torquey twin on the road, other than at very low speed or at a halt?

Race bikes demand different ratios.....close, then the high first becomes an issue that has to be fixed with more gears.....todays needs are different to yesterday's

Close ratio 4 speeders only ever worked for race bikes that needed to be push started, where the 1.8 ratio was a good choice for that....

Norton didn't change 2nd gear ratio because it was wrong!

Rohan · Dec 1, 2014

SteveA said:
Norton didn't change 2nd gear ratio because it was wrong!

So why did Nortons change 2nd gear then ?

It was to meet noise emissions, wasn't it ?
Raising it slightly meant the bike couldn't accelerate quite as hard - so it met the dBa specs.
This had the additional benefit that 2nd was now slightly closer to 3rd...

B+Bogus · Dec 2, 2014

Rohan said:
SteveA said:

Norton didn't change 2nd gear ratio because it was wrong!

Click to expand...

So why did Nortons change 2nd gear then ?

It was to meet noise emissions, wasn't it ?
Raising it slightly meant the bike couldn't accelerate quite as hard - so it met the dBa specs.
This had the additional benefit that 2nd was now slightly closer to 3rd...

Indeed. I seem to recall that it had to drive past the noise meter at 'X' revs in 2nd gear?
2nd to 3rd on the MkIIA on gearbox is pretty good - it's the gap back to 1st which is the PITA. I wouldn't consider 1st to be particularly low on a Commando either, compared to, say, a 5-speed Bonnie.
So lifting 1st gear would get things back in line... like a 4-speed CR box would :wink:

acotrel · Dec 2, 2014

B+Bogus said:
I agree that the standard gearing can be a handicap on anything other than town riding, which I avoid anyway.
I have to admit to being tempted myself for a while, and would still consider it as a compromise solution.

I find the gap between 1st and second can be a real pain even with a 21T sprocket, especially on downshifts (MkIIA, so I'm assuming the same as MkIII). The best way to avoid the back end squirming around seems to be to shift into first only when the revs have dropped right down, so the engine braking effect has pretty much gone, and not ideal for 'getting on with it' on my favourite roads
My Combat was great in this respect, but the gap to third felt too big (20T sprocket) - it might be just fine with a 19T, or with a less peaky motor.

I bit the bullet and bought a Quaife 5-speed, but as I haven't got my finger out to finish the bike yet I can't say how good it is. :roll:

I don't think you've got this quite right. The difficulty in changing from a relatively high second gear down to a low first lies in not having enough revs when you drop the clutch. You then try to accelerate the heavy crankshaft, and the rear wheel can chirp, or lock then slide. It is the reason slipper clutches were invented - so lazy people did not have to match the revs when changing down. The difficulty in using the standard commando box for racing is that you have to use too much throttle on the down changes, it is a bloody pain. The close ratio box is far superior except when using first gear in a clutch start.

Hobot · Dec 2, 2014

Amen on not downshifting with enough rpms to prevent sudden rear tire drag swing around & downs. THE Gravel taught me to be always be powering up/blip up on down shifts then easing off throttle so tire can catch up and engine drag lightens up. In 750 there's too much gap between 3rd/2nd so double trouble as rev's in 2nd not enough to be in good power band on up shift to 3rd and too much sudden drag dropping to 2nd. Switching 750's to 850's taller 2nd helps a lot for spirited action. Some the sweepers here require an up shift while leaned pretty far over which can be over exciting on some cycles like my SV650 or my factory Combat, sends a whiplash wiggle through frame that tends to hi side but not on Peel thankgoodness. Are-do you vintage or modern racers ever need & able to shift up while leaned over accelerating hard as can?

B+Bogus · Dec 2, 2014

acotrel said:
I don't think you've got this quite right. The difficulty in changing from a relatively high second gear down to a low first lies in not having enough revs when you drop the clutch. You then try to accelerate the heavy crankshaft, and the rear wheel can chirp, or lock then slide. It is the reason slipper clutches were invented - so lazy people did not have to match the revs when changing down. The difficulty in using the standard commando box for racing is that you have to use too much throttle on the down changes, it is a bloody pain. The close ratio box is far superior except when using first gear in a clutch start.

I think we're saying pretty much the same thing, but differently

Even blipping the throttle and feathering the clutch can still end up in a bit of crossing up squirreliness, and I've found the only way to be consistently smooth is to wait until the revs are right down in second before dropping into first - 2-up I generally keep the clutch in for a second or two before letting the clutch out in 1st.

Far from 'best practice', but keeps my pillion happy and oblivious.

Close ratio gear set

trident sam

johnm

olChris

acotrel

Matchless

acotrel

SteveA

Jagbruno

B+Bogus

Rohan

L.A.B.

Moderator

Rohan

L.A.B.

Moderator

acotrel

SteveA

Rohan

B+Bogus

acotrel

Hobot

B+Bogus

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