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Old 04-24-2005, 02:27 PM   #21
josephblow
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Default Re: Desirability of ABS brakes

I've been riding a R1100RT with ABS for the last 5 years; my first bike with ABS. I've only had a couple of instances where the ABS did its thing - and in both cases I know that if I had been riding the cruiser I traded in on the RT, I would have been on the ground or attached to the vehicle that stopped short in front of me. I don't believe that it gives me a false sense of security, however; most of the time I barely remember that the bike has ABS. Under normal or semi-urgent braking situations, the ABS never engages anyway...
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Old 04-24-2005, 05:15 PM   #22
nitrofly
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Default Re: Desirability of ABS brakes

I don't understand why an expert rider on a bike without ABS can outbrake a bike with ABS. If we put Valentino Rossi on a bike without ABS he will certainly be able to stop damn fast. However, we should expect him to stop just as fast on the same bike with ABS.



Why? The ABS will not engage until the wheel locks. Given that the Doctor is well known for being able to brake to the very limit *without* locking his wheel...the ABS will never engage and he will bring the bike with ABS to a stop in exctly the same time and distance as the bike without ABS.



If however Rossi just grabbed a handful on the bike with ABS...of course he would take a greater distance and time to stop.



So perhaps all bikes should be fitted with ABS because it won't ever be engaged until it is required non?
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Old 04-24-2005, 07:52 PM   #23
sportbikebandit
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Default Re: Desirability of ABS brakes

You make some good points. I guess if you are willing to spend the extra bucks say on a Honda VFR Inteceptor with ABS you can have a sport tourer you can take the ocassonal track day. However, the number of true replica racers with ABS I think is very small. So like I said if you are a canyon carver who wants the ablility to race you probably don't want ABS.

Especially if you to become the next Matt Mladin..
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Old 04-25-2005, 05:18 AM   #24
jungkvist
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Default Re: Desirability of ABS brakes

Again, as always, it's all relative.



Touring? ABS.

Sport tourning/Adventure touring? ABS, with on/off switch.

Sport bike? Rhetorical question, no-such thing.



Just stay away from Honda's linked brakes. With a little gravel on the road, those things make a 5mph turn an adventure.
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Old 04-25-2005, 06:52 AM   #25
bfulmer
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Default Re: Desirability of ABS brakes

I agree. I understand that performance sells and that race replica bike manafacturer probably don't want to take the hit for the additional weight, cost, and packaging. I wonder if the rules for racing organizations would force the race bikes to include ABS if it was offered on the production model?
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Old 04-25-2005, 06:56 AM   #26
bfulmer
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Default Re: Desirability of ABS brakes

This is the same post as above but you may have missed it.



It is a little complicated to explain but I'll try my best. The first thing you have to understand that tires experience "slip" every time you brake or acclerate (or turn for that matter). During braking, the presence of slip means that the tire is going a little slower the an unbraked tire. The level of slip depends on how hard you are braking. 100% slip the tire is locked and skidding, 0% slip the tire is "free rolling". For low slip values, the tire tread is actually being stretched at the tire-road contact. At higher slip values the rubber starts to skid across the road. Peak traction on concrete/asphalt occurs somewhere around 12% slip. So maximum braking occurs when both tires are at around 12% slip and stay there for the whole stop. The problem is that the tire is very unstable and non-linear at this peak slip value. Brake any harder and the traction will start to drop off and the tire will quickly go to lock. You have to be very good to maintain slip at this value. ABS will actually operate around this peak value most of the time and will actually cycle around the peak. Its about 95% efficient in doing this thus a perfect non-abs stop can still beat it. Its EXTREMELY hard to make this perfect stop!!! So in conclusion, ABS want's to operate at the same slip values as the expert, practiced, rider. So if you on a track and can hit the 12% every time on both tire simultaneously. ABS will not help. Any other situation, is a lifesaver.
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Old 04-25-2005, 09:18 AM   #27
motonut_1
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Default Re: Desirability of ABS brakes

Current ABS applications have a "leanometer". Once your angle of lean reaches a certain point, the ABS shuts down. The reason for this is that ABS's pulsations could complicate braking when leaned over. Of course if you've trail braked hard enough to kick in the ABS, you've already broken traction and most likely are on your way to kissing the pavement.



Most "road" riding schools will tell you to do your braking before initiating leaning into the corner and then accelarate through the corner. That way, you eliminate one set of traction variables while cornering. Expert roadracers oftentimes trail brake right to the apex of a corner and then actually turn the bike using the throttle. These are not recommended riding strategies for the road. With this in mind, I doubt that racers would allow themselves to have to contend with ABS on a race bike, so it's doubtful we'll see it on race-replicas.



BTW, both the BMW R1150/1200 GS series as well as the F650 had ABS that could be shut off. This would allow the rider to steer the bike by locking the rear wheel. BMW didn't link these brakes which was a good thing. I believe they have gotten away from that on their new models.
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Old 04-25-2005, 09:42 AM   #28
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Default Re: Desirability of ABS brakes

Thanks for the excellent explanation, seems like ABS is a no brainer indeed.
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Old 04-25-2005, 10:15 AM   #29
rick_1
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Default Re: Desirability of ABS brakes

Sean (Alexander), isn't the reason heretofore ABS bikes don't out shorter stopping distances is because the ABS computer is set for a maximum of 1-g deceleration? At 1 g of decel, you would stop in a best of 120 feet. The new Ducati didn't use this limitation and stopped from 60 in 113 feet, per MCN. Doesn't this negate some of your argument?
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Old 04-25-2005, 11:39 AM   #30
bfulmer
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Default Re: Desirability of ABS brakes

I've also heard this claim and wondered why someone would place a limit on deceleration. The only thing I can come up with is that this limit may have been there to ensure you keep the rear tire on the road. I know for a fact that the Ducati will allow a stoppie and will let the bike tip over forward. I've never actually tipped but came close enough to know that they will let it happen. It may just be a tuning philosophy? I think more sophisticated approach would be to limit deceleration only when a rear wheel lift is detected. ABS should be able to detect a rear wheel lift.
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