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Telelever vs Brake Dive?


BF204

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HI All,

 

Probably like most of you, I enjoy wrench turning and also learning about the technical aspects of my machine. I like how the telelever front end works, but conceptualizing how it works is on my list of "things that I don't understand"... (other examples include why spouses sometimes feel inclined to say the opposite of what they mean, and why pineapple gets put on pizza).

 

I've done my due diligence and searched this site, and also read whatever articles, and viewed whatever telelever animations I could find.... my bewilderment continues.

 

I understand that an upward movement of the telelever arm is translated into an arc movement of the front axle, and this would increase the rake as the suspension travels. What I don't understand is how the suspension geometry causes a reduction in brake dive. I've even read that the BMW engineers chose to leave some dive in, but that if the telelever geometry was changed, brake dive could be completely eliminated. (?) I'm not sure if that is true or not, but if it is, I take it that the elimination of brake dive is NOT related to changes in the rake angle, because the rake only changes as the suspension compresses (there would have to be some dive present to cause the increase in rake). Since the brake dive is due to weight shift, I don't see how you can eliminate it unless you had some other mechanical arrangement (like an Earles fork). If a front end only had a horizontal wishbone configuration (like a rear swingarm, flipped around and mounted on the front), I think (?) you'd still get brake dive since it would only be the suspension reacting to the increased force on the front of the bike from the weight shift (like pushing down on the bars), and I don't think it would matter whether the swing arm is horizontal, or suspension movement is inline with axle movement (like standard forks). I can push down on the bars of my telelever bike and cause the front suspension to rock up and down... why is the weight transfer during braking any different??

 

Anybody what to take a stab at enlightening me? If you don't succeed, don't worry, it'll be mostly my fault.. :dopeslap: In order to try and understand, and I'll re-read your replies with varying degrees of single malt intake to see if that helps.

 

Thanks in advance...

 

 

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HI All,

 

Probably like most of you, I enjoy wrench turning and also learning about the technical aspects of my machine. I like how the telelever front end works, but conceptualizing how it works is on my list of "things that I don't understand"... (other examples include why spouses sometimes feel inclined to say the opposite of what they mean, and why pineapple gets put on pizza).

 

I've done my due diligence and searched this site, and also read whatever articles, and viewed whatever telelever animations I could find.... my bewilderment continues.

 

I understand that an upward movement of the telelever arm is translated into an arc movement of the front axle, and this would increase the rake as the suspension travels. What I don't understand is how the suspension geometry causes a reduction in brake dive. I've even read that the BMW engineers chose to leave some dive in, but that if the telelever geometry was changed, brake dive could be completely eliminated. (?) I'm not sure if that is true or not, but if it is, I take it that the elimination of brake dive is NOT related to changes in the rake angle, because the rake only changes as the suspension compresses (there would have to be some dive present to cause the increase in rake). Since the brake dive is due to weight shift, I don't see how you can eliminate it unless you had some other mechanical arrangement (like an Earles fork). If a front end only had a horizontal wishbone configuration (like a rear swingarm, flipped around and mounted on the front), I think (?) you'd still get brake dive since it would only be the suspension reacting to the increased force on the front of the bike from the weight shift (like pushing down on the bars), and I don't think it would matter whether the swing arm is horizontal, or suspension movement is inline with axle movement (like standard forks). I can push down on the bars of my telelever bike and cause the front suspension to rock up and down... why is the weight transfer during braking any different??

 

Anybody what to take a stab at enlightening me? If you don't succeed, don't worry, it'll be mostly my fault.. :dopeslap: In order to try and understand, and I'll re-read your replies with varying degrees of single malt intake to see if that helps.

 

Thanks in advance...

 

 

Afternoon BF204

 

In concept it's really pretty simple. The angle of the lower control arm vs rearward loading of the arm during braking.

 

The length of the front control arm from front ball joint to rear mounting pivots & the height of the rear mounting pivots above the ball joint instant center & the tire contact point on the road all act together to force the rear of the control arm to try to lift higher & the front joint to try to go lower when a braking load is put on the control arm.

 

As an example (if you want some pain to get the point across) just take a 6' long 2x4 & place one end on your stomach the allow the other end to run along the ground in front of you. Walk or run with that angled 2x4 out in front of you until it catches in a sidewalk crack or in the soft grass edge.

 

I think that you will find that when that 2x4 catches & stops that due to the angle of the 2x4 having the front end much lower than the rear that not only will your body stop it's forward movement but it will also jack your body up as the rear of that 2x4 wants to travel in an arc up & over the lower front. (don't really do this as it is just an example to understand concept). Just picture a pole vaulter here.

 

Your BMW rear suspension acts about the opposite as the link angle vs swing arm angle & conflicting pivot points keep the rear of bike pretty even as the small pinion gear tries to climb the larger ring gear teeth on heavy acceleration.

 

BMW bikes with ABS brakes also allow a little more front end dive to be built into the front suspension as the BMW ABS system have an anti-lift algorithm programmed it that keeps the rear wheel from lifting (at least from lifting vary far for very long). Under heavy braking the ABS system monitors the front vs rear wheel spin down rates & if it sees the rear wheel decelerating too quickly vs the front it assumes the rear wheel is lifting off the ground so quickly removes some brake pressure. (on the BMW 1100 bikes this is VERY noticeable as the ABS-2 system is slow responding so the front brake release is harsh & abrupt so the bike can actually jump forward when the ABS tries to prevent rear wheel lifting.

 

The 1150 I-ABS system is much smoother & the 1200 bikes with the accumulator buffered front brake system is super smooth on the front release.

 

 

 

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Great explanation DR. I for one, love the Telelever system on my 1150. I take it for granted on most occasions (like so many things that are well engineered), but a long ride on my R90s soon reminds me. :)

 

RPG

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Lone_RT_rider
I take it for granted on most occasions (like so many things that are well engineered), but a long ride on my R90s soon reminds me. :)

 

It doesn't even take a long ride with my FLHTP to remind me. :) A short ride down I-41 here in Milwaukee reminds me very quickly.

 

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Thanks DR! What an excellent synopsis! I hadn't considered the upward/lifting force on the engine-side mounting end of the telelever. It acts like a lever... hey they should name it, oh... never mind...(insert Homer "duhhoh" here). I can wrap my head around your explanation and I spared my navel any experimental running around with a 2x4, but I may get my teenage son to try that while I sit on the deck and watch. I'll tell him it's a trendy new workout... the abdominal pole vault. :grin:

 

I appreciate the input...I won't appear to be such a dufus when someone asks me about the weird front end (with the naked bike, it's pretty much the first thing people comment on).

 

Cheers...

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Thanks DR! What an excellent synopsis! I hadn't considered the upward/lifting force on the engine-side mounting end of the telelever. It acts like a lever... hey they should name it, oh... never mind...(insert Homer "duhhoh" here). I can wrap my head around your explanation and I spared my navel any experimental running around with a 2x4, but I may get my teenage son to try that while I sit on the deck and watch. I'll tell him it's a trendy new workout... the abdominal pole vault. :grin:

 

I appreciate the input...I won't appear to be such a dufus when someone asks me about the weird front end (with the naked bike, it's pretty much the first thing people comment on).

 

Cheers...

 

Seems like in theory the Telelever should have some added rear brake capability under hard breaking VS a standard fork as front suspension dive is limited keeping more weight on the rear tire. Not sure if that has ever been documented in a shorter braking distance though.

 

I have gotten to really like the Telelever suspension, but I did need to get used to a sense of not being connected to the front wheel. Sort of like the lack of connection you have when driving the typical driving car. I just had to learn to trust the front wheel was out there doing its job. I will say that the sense of connection to the front wheel on the newest iteration of the telelever while not quite on par with a top notch telescopic fork is darn close.

 

I take it for granted on most occasions (like so many things that are well engineered), but a long ride on my R90s soon reminds me. :)

 

It doesn't even take a long ride with my FLHTP to remind me. :) A short ride down I-41 here in Milwaukee reminds me very quickly.

 

Haha HWY 41 between MKE in Germantown still has some nasty rough spots...as the long overdue resurfacing project creeps along.

 

I was going to make a wisecrack that the FLHTP has no front suspension travel giving the rough ride on HWY 41, but in fact the front suspension travel is within 0.1" of the R11xx and R12xx bikes (4.6" VS 4.7") The rear suspension travel (3.8" VS 5.3") and ground clearance (3.9 VS 5.4") is another story and may be part of the difference in ride quality. Suspension might need to be set up on the stiff side to avoid zeroing out on the ground clearance.

 

 

Edited by Paul De
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Lone_RT_rider
Haha HWY 41 between MKE in Germantown still has some nasty rough spots...as the long overdue resurfacing project creeps along.

 

Your telling me! That's my daily commute. The section just south of Pilgrim road is the worst. I've almost been thrown off the bike a few times riding that section. And that's with the FLHTP, which believe it or not has a full inch MORE suspension travel than the Road Glide special (and any of the touring/blacked out specials for that matter)! The first time I hit that rough section on a 2017 Street glide special, I literally got air off my seat. Made me a fan of long suspension travel really, really quick!

 

 

 

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