Hi, I'm getting ready to change my final drive ratio from 3.15 to 3.37 and was wondering how many out there have done it and how they liked it ? I found the 24 tooth compensator gear I'm still looking for the 37 tooth clutch basket. anybody out there.......?

 

Positive experiance, it will help by putting 5th gear closer to the sweet spot and keep from downshifting in some areas plus accelleration is better. I believe it adds 300 rpm at 55 mph, there is a formula (Andrews) but I think I'm close.

 

I have fitted a smaller compensator to my TC88, to reduce gearing. I have also revised the gearing on my Evo.

I suggest you leave your clutch as is and go down a further tooth on the compensator, which is much cheaper! What are your current compensator and clutch teeth numbers? Is your rear drive 32T/70T?

 

You gave me some advice about a year ago which helped me alot. Now I am in limbo over which compensation sprocket to go with between the 23 or the 22. If I am correct I am running a 25 teeth sprocket.
I have a 06 FLHX which has been thru a stage 3 upgrade. I want the more TQ but I want to be carefull about the lose of top end. Right now it will do about 115mph and I was wondering if I go with the 22 teeth sprocket will it drop me well under 100 mph top end on level ground.

Thanks for your time.

 

Pleased to be of assistance! I have a graph that will help with this. I produced it for another reason, so let me explain it.

The bottom green line shows a typical torque curve for a stock TC88, at the crankshaft, but related to road speed, not engine speed. The thick green line above shows the same bike, but with torque at the rear wheel, taking overall gearing into account. The top blue line shows torque at the rear wheel, but with a 21T compensator, while the red line shows the affect of a 6-speed over-drive gearbox.

What the graphs also show is the theoretical top speeds at peak rpm in top gear (5th for a TC88, 6th for the red curve). For a stock bike it is around 150mph, for my modified TC88 with 21T compensator it is 125mph. By 'theoretical' I mean what the speed would be if the bike could reach the red line rpm in top gear (which probably no modern Harley can do!).

Frankly, a dresser at speed is like a barn door from an aerodynamic point of view (no offence intended, as I also have one!). If you were to fit any compensator smaller than the stock 25T you will increase rear wheel torque and top speed should not suffer at all. It is very likely speed will increase a little with each tooth you take off.

With your modified bike you will have better torque figures than in my graph, but the principle remains the same. If you still use the stock red line your theoretical top speed will be the same as in my graphs. A 23T will reduce theoretical top speed to 23/25 x 150 = 138mph and a 22T = 132mph.

Many years ago a UK Harley owner tuned his Glide to give around 125bhp, with which it would do a claimed 125mph. But an unfaired Velocette 500cc single will do 100mph with just 34bhp, so you can see that getting a Glide up to high speeds is a power-hungry business! It needs three times as much power as a Velo to get a quarter more speed.

There is more discussion related to this in my Talk about torque thread. My 21T came as an SE kit with a shorter chain, which was an easy way of getting the parts together for my Dyna. It may still be available. I know from discussion here on HDF and elsewhere that many riders think it is too short and would rather raise gearing rather than shorten it, but I am very happy with my bike and the improved performance I get.

Whatever you chose to go with I think you will get a slight increase of top speed, you certainly won't lose any. With a 21T you might even get close to 125mph! Hope this helps.

 

You are the man.

THANK YOU.

 

my compensator is 25 and my clutch is 36. my front pulley is 32 and wheel pulley is 65 tooth for an overall 3.15 By changing compensator to a 24 tooth and clutch to 37 i will be at 3.37 which will get me up quicker and get into my andrews 46 cam earlier...I hope !

 

According to my maths your primary is 36/25 = 1.44 and secondary is 65/32 = 2.031. That gives an overall ratio of 1.44 x 2.031 = 2.925.

Fitting a 24T compensator and 37T clutch will change that to primary of 1.542 and overall of 3.131.

If you leave the clutch at 36T (that is an expensive part to buy), but change the compensator to 23T your primary would become 36/23 = 1.565 giving an overall ratio 3.179, which is very close (1.5%) to a 37:24, but will be cheaper to do.

A 22T compensator will give you primary of 36/22 = 1.636 and overall of 3.323, which is reasonably close to 3.37. A 21T compensator gives primary of 1.714 and overall of 3.482.

Hope that helps!

 

Hi, Thanks for all the info...it surely is appreciated! This whole thing got started after i talked to Bob Wood of woods cams,he recomended what i have above so anyhow i already have the ball rolling. I bought a brand new harley compensator for 69 bucks off ebay and the clutch basket for 100 bucks used locally, so i dont have too much into it........yet. I should have it done by end of next week. I hope it is what I'm looking for !!!

 

It is difficult to follow a thread when someone else interrupts the conversation.

Be considerate, start your own thread.

To the OP:

If you really want to go to the 37 tooth ring gear on a stock type outer clutch shell, you will be looking for a 1990-1993 clutch outer shell, and plates.

You would also need to change the inner hub to one used on years 1990-1997.