19” YZ wheel & Sprocket
So I’ve been running my 19” wheel for a while and I must say it’s got’s it’s advantages on and off road but I’ve been running the same gearing for the 18” wheel.
This had never really been an issue as I’d been riding the bike ver short distances and off road mainly. The lengthened 1st to 4th made for a lot of fun around trails and town + wheelies. However now I’ve been on some longer rides and had to use the motorway I can see that my bikes now struggling on the top end. 5th and 6th are still useable and you will enter power band but hasn’t got the steam to Rev out.
So long story short… how do I find found out what sprockets I need to run to go back to the original gearing?
It’s a standard DTR hub so WR200 520 sprockets etc are optional
And furthermore do the programmed powervalve opening’s effect/need to be different if I was to keep it the way it is?
I just buy the next 2 or 3 front sprockets with less teeth. Find which ones suits best JT’s are usually 6-7 quid each...
@SpookDog Those parasitic losses though
Go 412 pitch and renthal sprockets to minimise weight and losses.
I did go 520 myself back in the day, but now running stock 428. On my RS I went from the stock 520 to the GP Style 412 for less weight...
520 has no appeal to me. Extra weight + chains stretching has never been an issue (weird really because I used the same chain in my lexmoto adrenaline and always had that issue?)
I hadn’t heard of 412
I also know renthal do custom sprockets, it’s give me an excuse to support another reputable British company and get some more bling in the process
Calum last edited by Calum
@Stevie-Wonder 415 - I knew it was 41 something lol.
I used to have no end of chain stretching problems...but that was when I was a wee lad and didn't have a clue and bought cheap chains etc.
I thought you just wanted to get the gearing a bit ‘shorter’ in 5 + 6th? I have the same problem with my bike, until it’s running 100% right I don’t want to be ragging the balls out of it in 5 + 6th...
Trial and error with front sprockets. I have 13 to 17 tooth front sprockets ready for when my bike finally runs rite
@SpookDog The TZR 4DL Gearbox has a very narrow 5th 6th ratio. So might be worth getting that gearbox.
Noooo! I want to recreate the same ratio that was originally on the bike whilst still having the 19” rear as I know longer have an 18” to use anymore Does that make a bit more sense?
@Stevie-Wonder Yeah makes sense, just you may not be able to get the exact ratio since the jump in sprockets may not be granular enough.
markus.w last edited by markus.w
@Stevie-Wonder the way I see it you want to recreate the same gearing you had with your 18" wheel on a 19" wheel is that correct? If so doing the maths you'll need to know the circumference of both tyres and work out the difference as a percentage, for example if the 19" you have now is 5% bigger circumference than the 18" then to compensate you'll need to upsize the amount of teeth on the rear sprocket or downsize the front by 5% or as close as sprocket size options allow.
@Calum it might be worth building an 18” rear to use then, fucking about with sprockets is a pain in the ass.
Also my original tire size I was used to having when I was running my 18” rear was 120/100-18 or 140/80-18, I can’t remember exactly. All I remember was thinking bigger was better at the time of ordering them.
If I was to get an 18” wheel again I’d run 100/100-18 or alternatively 120/80-18 if I couldn’t find the previous size
@Stevie-Wonder I seriously doubt that you will notice that much of a drop in performance/top end with 1 inch wheel size and a different rear sprocket. So long as it's close enough you'll be fine.
@Calum sprockets are still the same, also you’d honestly be surprised the difference it’s not a huge one but it’s enough to completely change the way I have the ride the bike.
The gears as of a lot longer and are like a supersport 125, to get to the top end of your power band you really have to hold her WOT for quite a long time, because of this and the length of 4th and 5th you now can’t change into powerband to keep pulling in 6th.
Off road has a couple of advantages and makes the bike a little nicer to cruise on but overall it’s really not doing me or the bike favours
@Stevie-Wonder You do realise the wheels I'm running on my DTR right???
Seriously bud?! Building another wheel is less hassle than changing a front sprocket? I think you’re over thinking something here. Seriously, drop a tooth at a time till you’re happy...
You got sumo’s + 4DL trans aint you?
Dropping a tooth at the front makes the gears too short sadly, you'd need to adjust from the back which would require renthal making me a sprocket or somehow finding one.
Don’t get me wrong I’ve took the bike out a bit recently and changed the way I’ve been riding it and it’s been a lot of fun, it just requires more carefully timed shifting and clutch. Through 1st to 4th
Best way I could explain it is before on the original setup, it’s like you’d hit band in first then straight away shift into second then zip through the gears
As where now you get to power band and rather then zipping through you’re sat there letting it Rev and Rev waiting for it to reach to the end of the power curve so you can change up, it’s very reminiscent of a 4/ 125
Theoretically having that wheel should up the top speed but practically it’s made it slower
@Stevie-Wonder I wouldn't exactly call them Sumo and no I'm on stock DTRE transmission.
Aprilia RS 125 wheels and DTRE transmission. So it's a considerable change from the stock wheel setup and I think the gearing is fine. Tops out at about 70mph though but I'm not 17 anymore and weigh considerably more.
Rides lovely though and for zipping to and from town it's a perfect little bike.
Update the sidewall height of both tires I run on both wheels where the same, I’m not sure what an extra inch added equates to in terms of sprocket teeth but it explains a bit
Also no @SpookDog of course not, although I do need to buy a socket the right size that’ll fit the nut on the sprocket so I can experiment with a couple sprockets. Ya never know I might not be able to replicate the ratio but I could possibly get a nice medium between them both.
I think realistically though the stock gearing is the best without compromise for using the bike about town and off-road, which along with the occasional long road trip or weekend camping trip is what I need it for.
Also @Calum she sound good, may only do 70 but I bet she gets there pretty flipping quick
The difference between a 3.50 standard tyre and a 4.00 is a half inch. I corrected that gearing on my bike by dropping 1 tooth from 17 to 16. If you have a 17 front cog try searching ebay for a 15 tooth Jt front dtr125 sprocket. They are about 6 quid...
Whether you drop the front or raise the rear, its still the same. You are lowering the gearing. You want it 'shorter'...
As it happens I think I actually have a 15” sprocket in my garage, anyone know what size the sprocket bolt is?