BMW R1200R R1150R/T F800 K1200R R1100R/T R1250R RnineT Message Board

Dr. Strangelove wrote:I am thinking "Merc" = Mercedes Benz.

My bad, I was thinking Merc, as in Mercury....

Ron - it never even occurred to me that someone might think 'Mercury' when seeing 'Merc'. We never got Mercury's over here in the UK, so we'd automatically relate the term to Mercedes-Benz.

I got kinda confused when you said they'd stopped making them - but seeing as half the stuff with a European badge on it seems to be actually made in India, Brazil, China or Malaysia these days I didn't discount the possibility!).

grwrockster wrote:Ron - it never even occurred to me that someone might think 'Mercury' when seeing 'Merc'. We never got Mercury's over here in the UK, so we'd automatically relate the term to Mercedes-Benz.

I got kinda confused when you said they'd stopped making them - but seeing as half the stuff with a European badge on it seems to be actually made in India, Brazil, China or Malaysia these days I didn't discount the possibility!).

GRW, Now I see!...over here, 'slang' for Mercury was 'Merc' Strange how our country's are so similar & yet so different!...I learn something new everyday....

Ron

Only ever had slight speed wobbles with panniers and no rear luggage (top-box or the like).

I find the Top Box tends to smooth the airflow coming off my back and thus prevent speed wobbles starting.


GRW - you'll probably find that altering the bike's attitude to being tail heavy doesn't make a huge difference to the geometry - the Telelever arm will mean the trail (?) if anything will get shorter when the tail is heavy - and when braking heavily (loading the front) the trail will increase. Depending obviously on where the Telelever arm is in it's arc of movement - which in turn will be related to the length of the front shock at the time.


ie - the Telelever system won't definitely extend the wheelbase when the forks are more extended, like regular telescopics.

Hmm. RB - you're right - I hadn't considered the effect of the movement in the bevel box pivot on the wheelbase.

I'd been thinking more about the headstock angle - ergo the angle of the forks tbh - if the rear sits lower (as it must do as my feet are flatter on the floor with weight on the back) ergo the forks must be raked out more (i.e. the headstock is rotated rearwards and is therefore further away from the front wheel spindle - so a shallower steering angle and corresponding additional stability was my thinking?). So, the steering should be slower (although after your input I can see that this might be altered or negated by a change in wheelbase induced by the paralever).

I've never run with the cases on without the top-box on as well, but I can see the sense in your statement, what with the top-box acting almost as a fixed 'tail' out the back to stabilise things. But the big weave I got on the autobahn (with a box on) was real enough (an increasingly bigger handlebar arc and corresponding weave from side to side that didn't stabilise, so I didn't push it further).

There was hardly any weight in the top-box btw - I tend to keep light stuff sticking up there for obvious reasons.

I think I'd be a bit surprised if you could get one of these things to tank-slap hard enough to lose control completely (unless of course, someone out there knows different ). Also my bike, being fitted with 'GS 'bars and a 'bar mounted screen is a bit more 'lively' than stock too, so standard bikes are probably a bit better than mine in this respect I'd guess.

My weave was severe enough at 110mph-ish to make me take stock and rethink, but it wasn't a full-on rapid lock-to-lock headshake (like I've experienced on something more sporty when accelerating hard over a bumpy section of road). So I had no qualms about winding it on again with a modified approach to keep it stable.

Maybe it's the weight thing then? Whatever, the thing seems totally stable with the missus sat on the back .

grwrockster wrote:Hmm. RB - you're right - I hadn't considered the effect of the movement in the bevel box pivot on the wheelbase.

???? That's at the back - I'm talking about the Telelever arm at the front!

Although I'll admit I hadn't thought about the change of angles within the Paralever (rear system). IIRC through they don't tend to change the wheelbase too much.

grwrockster wrote:I'd been thinking more about the headstock angle - ergo the angle of the forks tbh - if the rear sits lower (as it must do as my feet are flatter on the floor with weight on the back) ergo the forks must be raked out more (i.e. the headstock is rotated rearwards and is therefore further away from the front wheel spindle - so a shallower steering angle and corresponding additional stability was my thinking?). So, the steering should be slower (although after your input I can see that this might be altered or negated by a change in wheelbase induced by the paralever).

I've never run with the cases on without the top-box on as well, but I can see the sense in your statement, what with the top-box acting almost as a fixed 'tail' out the back to stabilise things. But the big weave I got on the autobahn (with a box on) was real enough (an increasingly bigger handlebar arc and corresponding weave from side to side that didn't stabilise, so I didn't push it further).

There was hardly any weight in the top-box btw - I tend to keep light stuff sticking up there for obvious reasons.

I think I'd be a bit surprised if you could get one of these things to tank-slap hard enough to lose control completely (unless of course, someone out there knows different ). Also my bike, being fitted with 'GS 'bars and a 'bar mounted screen is a bit more 'lively' than stock too, so standard bikes are probably a bit better than mine in this respect I'd guess.

My weave was severe enough at 110mph-ish to make me take stock and rethink, but it wasn't a full-on rapid lock-to-lock headshake (like I've experienced on something more sporty when accelerating hard over a bumpy section of road). So I had no qualms about winding it on again with a modified approach to keep it stable.

Maybe it's the weight thing then? Whatever, the thing seems totally stable with the missus sat on the back .

Ah. RB - I'd disregarded the front-end from the point of view of extending or compressing fork length and the effects, and changes in wheelbase as well. Especially as we are talking about straight and level forward movement, and relatively slow accelleration over the ton as the circumstances (so the suspension will be pretty settled anyhow).

My view was very simplistic - if the attitude of the bike is changed (i.e. the rear end is lower due to added weight - although it should be equally true if lowered by any other means) then it seems to me that the effect has to be to open out steering angle. My understanding was that an increased distance (front-rear along the ground axis, not in a straight line from headstock to spindle) between the front axle and the steering head (which must be the case if the rear of the bike is lower, as the headstock is rotated away and downward in an arc around the front wheel spindle, yes?) will tend to make the bike more stable in a straight line, and harder to turn (such as the extreme examples of sportsbikes and cruisers like HD's ).

I'm no steering geometry boffin though, so am quite happy to be both educated and corrected !

grwrockster wrote:Ah. RB - I'd disregarded the front-end from the point of view of extending or compressing fork length and the effects, and changes in wheelbase as well. Especially as we are talking about straight and level forward movement, and relatively slow accelleration over the ton as the circumstances (so the suspension will be pretty settled anyhow).

My view was very simplistic - if the attitude of the bike is changed (i.e. the rear end is lower due to added weight - although it should be equally true if lowered by any other means) then it seems to me that the effect has to be to open out steering angle. My understanding was that an increased distance (front-rear along the ground axis, not in a straight line from headstock to spindle) between the front axle and the steering head (which must be the case if the rear of the bike is lower, as the headstock is rotated away and downward in an arc around the front wheel spindle, yes?) will tend to make the bike more stable in a straight line, and harder to turn (such as the extreme examples of sportsbikes and cruisers like HD's ).

I'm no steering geometry boffin though, so am quite happy to be both educated and corrected !

If we were talking telescoping forks that only extend and retract in one plane, then you'd be right. But the Telelever system, as I say, rotates the front wheel around the pivot point in the engine cases, so it's not as clear cut.

If we were talking telescoping forks that only extend and retract in one plane, then you'd be right. But the Telelever system, as I say, rotates the front wheel around the pivot point in the engine cases, so it's not as clear cut.

Sorry RB - still confused.

Please note - I'm not talking about forks extending or compressing - I'm talking about flat and level travel (as the bike was on a flat, level road with steady acceleration). Granted the forks may be extended slightly, but if we disregard fork travel completely as it's clouding things for me here - I can't see the relevance of the front-end action or it's suspension arm might significantly affect how more weight lowering the rear affects stability at all.

I can't see how the forks actuate having a direct bearing on that (as with any suspension on a steering angle, then as suspension extends or compresses it has an effect on wheelbase but more importantly as I understood it - steering angle (e.g. fork dive pitches the front-end downward, which steepens the steering and makes it faster to turn and therefore less stable). But we aren't talking about hard braking and how telelever minimises fork dive etc.

The forks pivot off the engine cases yes - but I fail to see that this has any effect on what I thought was the fundamental aspect - the angle of the forks. I cannot see that telelever has any effect on the steering head angle and therefore this aspect (high-speed stability) under these circumstances at all? The steering head. yokes etc. do not move but are in a constant fixed angle related to the the rest of the bike, yes? Therefore, if the bike is lower at the rear, then the fork angle in relation to the floor alters, the distance along the ground between axle and steering head lengthens and becomes a more stable, slower-steering (more chopper-like if you prefer) arrangement.

I keep coming back to... lower rear end = changed fork angle = more stability (and vice-versa). As simple as that. I'm trying to think about what you're saying about telelever and how this might change things, but I really can't see what you're getting at. The engine case pivot point seems to me to be just a leverage point so that the suspension arm has a fixed point so that the shock is operated by the fork tube movement. I can see that this aspect is just like a swinging arm, except that the telelever works over a very short travel, and the forks are fixed and triangulated to the steering head - so it seems to me that the angle of the forks cannot be altered at all by telelever in this aspect (and neither could conventional forks - a fixed steering angle is fixed - I can only see that changing the whole attitude of the bike e.g. raising or lowering the rear will do this.

That's the only sense I can make of it. I'm certainly not saying that you're wrong - I'm not confident enough in my own rationalisation to be that dingle. What I am saying is that I really don't get what you're telling me.

110 mph in the empty wilds of Nevada. Very fully loaded. To full actually.
For all the LEO's out there: just kidding...

disregard last post

grwrockster wrote:

If we were talking telescoping forks that only extend and retract in one plane, then you'd be right. But the Telelever system, as I say, rotates the front wheel around the pivot point in the engine cases, so it's not as clear cut.

Sorry RB - still confused.

Please note - I'm not talking about forks extending or compressing - I'm talking about flat and level travel (as the bike was on a flat, level road with steady acceleration). Granted the forks may be extended slightly, but if we disregard fork travel completely as it's clouding things for me here - I can't see the relevance of the front-end action or it's suspension arm might significantly affect how more weight lowering the rear affects stability at all.

I can't see how the forks actuate having a direct bearing on that (as with any suspension on a steering angle, then as suspension extends or compresses it has an effect on wheelbase but more importantly as I understood it - steering angle (e.g. fork dive pitches the front-end downward, which steepens the steering and makes it faster to turn and therefore less stable). But we aren't talking about hard braking and how telelever minimises fork dive etc.

The forks pivot off the engine cases yes - but I fail to see that this has any effect on what I thought was the fundamental aspect - the angle of the forks. I cannot see that telelever has any effect on the steering head angle and therefore this aspect (high-speed stability) under these circumstances at all? The steering head. yokes etc. do not move but are in a constant fixed angle related to the the rest of the bike, yes? Therefore, if the bike is lower at the rear, then the fork angle in relation to the floor alters, the distance along the ground between axle and steering head lengthens and becomes a more stable, slower-steering (more chopper-like if you prefer) arrangement.

I keep coming back to... lower rear end = changed fork angle = more stability (and vice-versa). As simple as that. I'm trying to think about what you're saying about telelever and how this might change things, but I really can't see what you're getting at. The engine case pivot point seems to me to be just a leverage point so that the suspension arm has a fixed point so that the shock is operated by the fork tube movement. I can see that this aspect is just like a swinging arm, except that the telelever works over a very short travel, and the forks are fixed and triangulated to the steering head - so it seems to me that the angle of the forks cannot be altered at all by telelever in this aspect (and neither could conventional forks - a fixed steering angle is fixed - I can only see that changing the whole attitude of the bike e.g. raising or lowering the rear will do this.

That's the only sense I can make of it. I'm certainly not saying that you're wrong - I'm not confident enough in my own rationalisation to be that ----. What I am saying is that I really don't get what you're telling me.

The bit in bold -is a "no". The steering head angle does change - it has to - think about the movement of the front swing arm - as it rotates it's end is moving relative to the steering head. The forks compress/extend to accomodate this (compressing the shock in the process), but the angle between the main frame and the forks will change. The forks are not fixed hard into the yoke at the steering head - they're in (IIRC) a rubberised pad that allows them to change angle (even though they're bolted to the yoke).

If the forks WERE hard bolted into regular yokes like telescopic forks, then the suspension would be locked solid, it wouldn't be able to move because there would be too much stiction in the sliding tubes.

Further, under heavy braking, although the forks compress, the wheelbase actually extends, thus making Telelever bikes more stable under heavy braking. As the swinging arm comes up, it pushes the front wheel away from the bike.

That's why I'm saying that under heavy rear loads you might get slightly more instability in the bike. But the system is so stable anyway that (imho) it's unlikely you'll ever get more than a slightly twitchy feeling through the bars. In your case this would be exacerbated by the GS bars and high, steering mounted screen that will enhance any movements caused by airflow.

AH! I wondered about the headstock for the reasons you mention, but couldn't see or even imagine that (or quite how) the headstock angle could or would change. I was thinking that perhaps the range of movement of the telelever arm was so small that it was taken care of by careful geometry by the factory, and any (very) small deviation absorbed by the telever ball joint rotation, and that the steering head didn't need to move at all as a result. But I can fully understand what you're saying about increased wheelbase, steering angle and stability with the head angle pivoting.

I'm with you on the overall stability - even when I got a bit of a weave on (and yes, my bike is bound to be a bit more lively than stock as well), I never felt that it was going to get out of hand. Safe as houses.

I always found that my 2003 1150R was more stable with the extra-wide lids on. I've done max speed, or almost, with them on. No issues.