The wedge shape of the slider allows the variator to actually open a bit wider at rest, dropping the belt into a smaller circumference between the variator halves, essentially lowering your gearing from a start and helping with off the line acceleration. As they are lighter than stock, your bike is revving higher, closer to it's torque peak and can apply more force through that lower gearing, hence the two-pronged increase in performance.
The same wedge shape also does the converse, at high speed, forcing the variator halves closer together than before, effectively raising your gearing and lowering rpms, even with lighter weights. Brilliant design.
The standard rollers (which actually also slide, not "roll", are fixed diameter, with taller gearing from the start and lower gearing at speed...
Thanks for your reply."I just replaced the rollers and sliders on my BMW c650gt with 28gr Dr Pulley and I’m not happy ... There is some lag at start ... the rpm is super high at all times. Is that normal??"
I replaced mine two weeks ago with a new belt (2013 GT with 15,000 miles). I had a similar reaction. The rev's seem high, though it's hard to be precise with BMW's bar system, with each bar spanning 1,000 rpm's.
This was a definite culture shock for me coming off a 2016 Burgman 650 -- Suzuki's SMART transmission has that bike at 3,000 rpm's for 50 mph and 3,500 for 60 mph like clockwork. Amazing transmission. Unfortunately, it has a belt buried so deeply it takes a master mechanic to replace or $4,000 at a dealer. The Burgman also handles like a bathtub on wheels at low speed. I owned three and STILL can't turn around on a two-lane road without putting my feet down. That's never a problem with the BMW.
I noticed the same lag when starting out. Some of that comes from Gen 1.0 models, pre-2016. I owned 2016 and 2017 GT's and takeoff was WAY better. I've been living with the lag on my 2013, thinking it was normal. Maybe the sliders made it worse? I can't tell.
One BIG positive is the bike now ZINGS when I accelerate quickly over 20 mph. If I twist the throttle hard, it's hold on to your hat time. The bike is a rocket, quicker than my '16 and '17 were. It takes off faster than the Burgman's Power button, which basically drops gearing by 1,000 rpm's to work like "Turbo" mode. I really enjoy the enhanced acceleration.
Not sure I'd put the sliders in again. Not sure I want to change them back. Eventually I'll end up with a low mileage '19 or '20 and I'll see how that performs. I have a feeling I'll like it just fine, as-is.
Lol, yes. Hopefully I’ll go back to nice and quiet ride. I thought and as I read here people were saying that acceleration is better but you get lower rpm at higher speeds which is not the situation in my case. And as I did the service at a BMW dealership I don’t think they did something incorrect. Its 2016, I just did the 12k service."I think I’ll go back and replace with the oem ones"
If you do, please share your thoughts here. That would be an excellent "before and after" test, although an expensive one for you.
What year is your C650 GT?
Wow, hope you had a nice ride. As I mentioned I did the 12k service today and replaced the belt with Malossi and dr Pulley rollers and sliders. I’ve read all great reviews and when I took the bike I was shocked. I don’t know what could be the problem. When I rev up from 0 it has a little bit of lag and then it goes to 5k rpm and it doesn’t move from there even on 70-80mph. I also notice that it disengage at 15mph when I release which is so bad as in NYC most of the time we ride slow.You piqued my curiousity about rpm's and what is normal, so I took a run down I-95 this evening ....
Like most of South Florida, it's a flat road, so it's easy to get a good idea of what's happening with rpm's without factoring in climbing or descending grades.
I rode for several miles at 70 to 80 mph and the bike had a ceiling of 6,000 rpm's, which could have been 5100 or 5500 or 5900, given BMW's maddeningly imprecise tachometer. When I reached 50 mph, the bike went to 5,000 rpm's. At 40 mph it was 4,000 rpm's. At 30 mph it was 3,000 rpm's, and 2,000 rpm's at 20 mph. That tidy correlation stayed the same whether I increased or decreased speed.
That's my version of what is normal for Dr. Pulley 28 gram sliders (and insert pieces -- I've heard they make a difference). For "test" purposes, the rest of the bike is tip-top and up to date ... good tires, new belt, new engine oil and filter, new air filter and CVT filters, new coolant and new spark plugs.
As for loud, it's just kind of a loud, growly BMW bike. I'd suggest foam ear plugs, if you don't wear them already. I never ride this bike without them.
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