Apex turbo Gearing w/8 tooth Drivers

[Adrenaline Addiction]

I am looking to gear down my Turbo Apex without having to change my new chain, I want to drop about 10 MPH. I used the Turbo Addiction calculator and found stock gearing with 3 pitch 8 tooth drivers, 20/40 gearing is 99.97 mph. Would any of the following gearing configurations work with the stock Yamaha chain and fit in the chaincase? Yamaha doesn't seem to sell much for gearing but I see MPI has everything mentioned below.

18/40 would be 89.98 mph. My preference.
19/42 would be 90.45 mph.
19/43 would be 88.35 mph.

Thx, AA

 

[aja636]

On a boosted sled, just a question, what are you doing for traction? Gearing that low, with this power level??? I had 25/38 gearing on 9 tooth and did nothing but spin the track everywhere.
Just food for thought...

 

[kinger]

Wow that is some LOW gearing. Did you check the gearing calculator in Ulmer racing section. I use that to plan my driver, and gearing needs.

 

[Adrenaline Addiction]

18/40 with 8 tooth is approx the equivilent of stock 20/40 with the 7 tooth drivers. I am running 162 2.5 track, this is a mountain sled, I dont need over 90 mph.

thx, AA

 

[TBird]

I would never, ever, choose such small gear as 18.
But, without changing chain i don't believe you can choose 19/42, else that would be my choise,

 

[Adrenaline Addiction]

I would never, ever, choose such small gear as 18.
But, without changing chain i don't believe you can choose 19/42, else that would be my choise,

I gave MPI a call, they said I could run the 19/42 with the stock chain.

They have a great chart showing what configurations work. I agree, I'd be a little worried about the stress on the chain with an 18 tooth top gear.

http://www.mountainperformance.com/yama ... _chain.htm

Thanks for the speedy replies.

AA

 

[mulot30th]

I do have apex turbo 174" extreme camoplast.

and I don't see any reason going that low on gearing.

7 tooth drivers and looking to run 23/40 or 23/38 gearing.

 

[TBird]

Ok, chart says 70L chain, but if they says 68L work they must have tried.

 

[Adrenaline Addiction]

Ok, chart says 70L chain, but if they says 68L work they must have tried.

Thanks for looking, they told me it worked but their chart says no, just changed and ordered the 19/41. He must have thought I had a 70 L chain.

 

[rx1 fern]

what would you recommend with 8 tooth drivers and a 144 track in a 2inch lug.would you go with a 24/38 or a 25/38.this is for an 04 rx1 with a front mount turbo.i want an aggressive hole shot.

 

[aja636]

some of us are flat land guys, that have no idea what mountain set ups are, do what you got to.. and never mind us.

RXfern I would go with 25/38 for what you are doing and you will like it just the right amount. Pay attention to clutching and she will pull hard to about 115-120 with 8 tooth and that big track. She will give you al the holeshot you need at that!

 

[RED]

I run 20/43 with old style 9t 2.52" drivers which is about the same a the new 8t 3" ptich drivers, this in the mountains of bc. Belt is happier, has lots of grunt on the bottom, there isnt really many places out west to let a turbo sled loose. Other than the glaciers of the whislter area. That place is massive.

 

[Adrenaline Addiction]

Thats what I'm after is a happier belt, takes alot of HP to plow around the steep and deep, throttle response is king.

 

[Rx1M5]

I run 19 40 with reverse on a boosted Rx1 dropped and rolled and 8 tooth 3.0 pitch drivers. I used to have 19 42 before I added reverse and it worked pretty well but the 19 40 system has been fine on belts and pulls down low no problems. I'm upping the boost this year so that may change.

Rx1M5

 

[Racegun]

Has anyone in the Mtns. gone as low as 19/42 with 7th drivers? I took the MPI 8th drivers off and put Avid 7th on and they are a lot smaller. 162 x 16 x 2.5 3"