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Anyone put -1 front sprocket on a 2015+?

14K views 51 replies 15 participants last post by  Tahoebrian5 
#1 ·
Would love to know your thoughts on it, especially from a street riding viewpoint
 
#2 · (Edited)
I did a 520 conversion with -1 in front. Acceleration is great. I still hit 186mph. Keep in mind I'm ~185lbs with gear. I have a sprint filter and a Racefit slipon, IAT relocation mod (really like this mod).


Other riders with RR 15+ go crazy wondering why I can pull away faster than them.

My only issue with 520 conversion is the chain, when you do -1, chain becomes longer. So my wheelbase is about 2cm longer now. It's good for stability and reduces wheelies coming out of turns. But it makes turn in harder. @d40 has the same chain I have. He removed another link from it, his system has a ~1cm shorter wheelbase. Not sure if his bike wheelies more or not. But it would turn in faster.

Bottom line I would do 520 conversion, -1 in front. I went with Alpha sprockets, and DID gold ZVMX 120 link chain. You might want to remove a link from it depending how you like your wheel base. I think I'm going to remove one from mine. I prefer a shorter wheelbase.

DID 520 chain is about 3lbs lighter than OEM one. Sprockets are also lighters (did not weigh them). But noticeable when holding one in each hand.
 
#3 · (Edited)
I did a 520 conversion with -1 in front. Acceleration is great. I still hit 186mph. Keep in mind I'm ~185lbs with gear. I have a sprint filter and a Racefit slipon, IAT relocation mod (really like this mod).


Other riders with RR 15+ go crazy wondering why I can pull away faster than them.

My only issue with 520 conversion is the chain, when you do -1, chain becomes longer. So my wheelbase is about 2cm longer now. It's good for stability and reduces wheelies coming out of turns. But it makes turn in harder. @d40 has the same chain I have. He removed another link from it, his system has a ~1cm shorter wheelbase. Not sure if his bike wheelies more or not. But it would turn in faster.

Bottom line I do would 520 conversion, -1 in front. I went with Alpha sprockets, and DID gold ZVMX 120 link chain. You might want to remove a link from it depending how you like your wheel base. I think I'm going to remove one from mine. I prefer a shorter wheelbase.

DID 520 chain is about 3lbs lighter than OEM one. Sprockets are also lighters (did not weigh them). But noticeable when holding one in each hand.
Thanks for that z00. Yeah i definitely don't want to increase the wheelbase so I'd either remove a link or get a shorter chain.
I'd prefer to keep the wheelbase stock spec actually
 
#16 ·
+2, damn you're brave lol

Keep us posted how renthal works for you. I read mixed reviews.

Cyclegear has a nice chain tool for a good price. Be sure you have an extra chain master link in case you screw up.

Knowing what I know now, I would drop one link from ZVMX 120 chain. Now sure how that will work since you're adding +2 in the rear, I say test it out first before pressing the master link pins to ensure the length is at what you like. Don't go by comparing OEM chain to 520 one, go by testing wheel base mounted.
 
#21 ·
I have gone -1 on my 15rr and have found it lengthens the wheelbase by approximately 7mm. which is coincidently one length on the swingarm adjuster lines. (line to line)

I have just now ordered a rear 46T 525 to fit the HP wheels from Alpha racing in Germany. This extra tooth in the rear +1 from the OEM 45T should bring me back to approximately the stock wheelbase setting.

As the -1 alone makes the 15rr turn in like a Pig, and is basically a **** feeling for fine control.

Someone on this thread mentioned that going -1 up front created about a 2cm increase in the wheelbase from stock. I believe this may be incorrect and am now worried that my workings out for the increase was incorrect.

Could someone on here with a bigger brain please correct me or the other guy.

-1 up front on a 15rr is worth about 7mm in wheelbase increase from stock... is this correct or incorrect.?....

Some of you guys on here are pure genius.

going -1 up front and +1 in the rear with the stock chain, to me should equate to almost the same wheelbase length as stock...RIGHT.... hope I'm right.
 
#23 ·
I have gone -1 on my 15rr and have found it lengthens the wheelbase by approximately 7mm. which is coincidently one length on the swingarm adjuster lines. (line to line)

I have just now ordered a rear 46T 525 to fit the HP wheels from Alpha racing in Germany. This extra tooth in the rear +1 from the OEM 45T should bring me back to approximately the stock wheelbase setting.

As the -1 alone makes the 15rr turn in like a Pig, and is basically a **** feeling for fine control.

Someone on this thread mentioned that going -1 up front created about a 2cm increase in the wheelbase from stock. I believe this may be incorrect and am now worried that my workings out for the increase was incorrect.

Could someone on here with a bigger brain please correct me or the other guy.

-1 up front on a 15rr is worth about 7mm in wheelbase increase from stock... is this correct or incorrect.?....

Some of you guys on here are pure genius.

going -1 up front and +1 in the rear with the stock chain, to me should equate to almost the same wheelbase length as stock...RIGHT.... hope I'm right.

Not that I believe I am one with a bigger brain but, sometimes typos are self evident.

Sometimes it's not a typo at all, and the source need only be considered to validate/invalidate the comment(s).

There are a lot of variables at work when you change the sprockets, you may not be changing just the gear ratio on your bike.

There's a bit of geometry to be aware of, and I struggled with that in high school, so I'm not a good source to explain that topic and how it could play itself out, if done to an extreme from the OEM specs.

Also the radius the chain will wrap around the front sprocket versus the rear sprocket is not equal, so saying -1 on the front and + 1 on rear should be "even-steven" or "close" wouldn't be something I'd bank on.

Like @skapan said get an extra master or 3, and be happy.

Most of all, you need to decide for yourself, independently of whatever is said by whomever (especially on the internet) what is right for you. My post(s) as well.

YMMV and good luck with further sound research.
 
#22 ·
Why worry about it, buy another master link and cut the chain. Then you can have the sprocket ratio you want AND the wheelbase you want.
But I can't see 2cm from taking one tooth off the front. One line maybe. And adding one to the back will not change it much, after all it's only a 2 or 3 per cent increase.
 
#24 ·
Thank you guys, you have brought up some points I have not really considered.

I guess I will know how close or far off I am from stock wheelbase once I install the 46T.

Either way the way it is now is way to long for me.

I know I'm going to like the -1 +1 combo.

Fingers crossed I guess that I don't have to mess around with the chain links.

we will see.

You guys always bring up great points, Thanks Again.:grin2:
 
#25 ·
Some good points brought up here. I'm planning to order a -1 front 525 pitch to run with my stock chain and rear but I certainly don't want a longer wheel base. If anything I'd prefer it a touch shorter as turn in feels a bit slow as it is in stock form. It sounds like going minus 1 will increase 2mm. If I remove a link from the chain, I haven't measure this but that is a pretty big difference and not sure that's going to work. Thoughts? I'm wondering now if I will be better of just doing a full 520 conversion
 
#35 ·
so...

If you take a new bike without any stretch in the chain and you measure the wheelbase or take the measurement from the rear axle marks(lines) and keep the slack in the chain in the same position for the -1 +1 change, then will that equate to the same wheelbase or measurement from the rear lines next to the axle nut.?

anyone.

I'm thinking the wheelbase will be the same as stock or awfully close if you go -1 +1 with the above considerations.

-1 alone is terrible for tip in. feels like a pig.
 
#42 ·
Not sure if +1 in rear sprocket will make wheelbase like stock. But it will make number of teeth even on both sprockets, which is not recommended. There was a separate thread on that elsewhere on here.

I would just remove one extra link from the chain, wheelbase will be shorter than stock. Instead of +1 in rear sprocket.

This got me thinking what is exact effect on tip in and bike stability (coming out of turns) for increase or decrease in wheelbase. BMW must have a formula to pick ideal wheelbase length, anyone has an idea how they go about that?
 
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#41 ·
What about riding below sea level? Like in lowest area on earth, around deadsea in Jordan. Do we get or lose power going the other direction?
 
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#43 ·
Okay, the question now is what combination of sprockets or pitch will gain acceleration without reducing the wheelbase.
 
#45 ·
I will let you know once my Alpha rear 46T 525 HP4 sprocket arrives.
It will bring the wheelbase in shorter non the less but by what. I'm figuring about 7mm. which for me is back to my best position.

And yes how the heck does BMW formulate the stock wheelbase, because it feels perfect.
 
#46 ·
Is not 7mm shorter wheelbase is about what d40 mentioned he got his wheelbase with only -1 and removing one chain link? So I'm confused on why you need +1 in rear to get that. Nonetheless, keep us posted, curious what you find out.
 
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