Switching to non-telelever front forks

[Sander Abernathy]

So repairing my five week old bike with OEM parts is going to run over $10k for the parts alone. The problem is the OEM front forks which are more than half of that number. BMW can charge what they want for them because there is no alternative in the marketplace. If we were talking about a sportbike with a non-telelever front-end I could get Ohlins for half of what BMW charges for the R12R forks and the Ohlins don't require an $850 trailing arm and a $1,000 strut.

So, I'm thinking of having someone fabricate a front frame that will allow me to attach a normal triple clamp and non-telelever forks. To get an idea of what I am thinking (copying) take a look at this site:

http://www.motorcycledaily.com/2008/11/ ... mwconcept/

Share your thoughts. Encourage me. Dissuade me. Reaffirm that I'm an idiot. Recommend someone that can make it happen. All input is welcome.

Sander

[mogu83]

I have a springer front fork from an old BSA , I even have a drum brake (vintage 1942) that will mount on it so you can do away with those pesky ABS brakes. A little welding and your good to go.

[boxermoose]

Beemerbone yard......

[ka5ysy]

Beemerbone yard......

+1

[Catchina]

The unique suspension is a HUGE part of what makes BMW bikes what they are...restore the telelever otherwise I would also say Beemer bone yard.

[dbrick]

I like the Telelever, replacing it even with expensive parts will be easier than the alternative design-and-fabricate route, and I'd guess that stock will give you a better motorcycle than home-brew engineering.

But...those beefy forks look really good.

[hjsbmw]

Assuming your insurance doesn't pay I'd also go the used route. Beemerboneyard and eBay have both listed those parts in the past. It would mean waiting for them to be available though.

As others have said, the front suspension is also for me one of the big pluses on this bike. Not having the dive when I break feels so much more stable and confidence inspiring. Riding with a conventional fork recently felt as if something was broken.

[mogu83]

Seriously,
One thing I've learned about motorcycles over more than a few decades of riding and working on them is to be extremely careful of any changes in the geometry of the machine. If you screw with the brakes the worse result would be you do not stop or the brakes could lock up, both events could be a disaster but not likely. Screw with the engine and it could stop. Incorrectly install farkels and they could fall off or electrical errors could destroy components. But fool around with fork rake angles, fork trail, swing arm lengths and angles, tire type and size or swapping suspension parts might well put you in a situation where the bike suddenly throws you on the ground at a very inopportune time. (like in the middle of a high speed turn or hitting a pot hole at speed).
The formula for a well handling motorcycle has been developed over a century of engineering and on street experience and just increasing the tire size or changing the rake by a degree could have a major effect on how some bikes handle. Bikes like the one in the picture look cool but taking one out on the road and riding it hard (not putting around a parking lot like the builders usually show) might put a rider at risk. I'm not saying these modifications can't be done, but they should be done by someone that really knows what their doing not by some shade tree guy with a torch in his hand.
As an aside: A bunch of years ago I built a Yamaha SR500 café racer, put on a dual disk front end from a 650, an extended swing arm with a disk brake from something, larger diameter tires and a severely modified engine. The thing sounded great, looked mean and ran strong in a straight line, but as soon as you tried to turn, even a sweeper at moderate speed, the thing would go into a tank slapper. Nothing would fix it - I striped the good stuff off and rolled the frame into a junk yard (breaker) .

I thought this thread was a joke - but maybe not. Bottom line what you propose could be done, but to be done correctly would most likely cost twice what the bike is worth and surely more than a new bike.

Naturally IMHO

[Sander Abernathy]

I asked for feedback of all sorts including critical so thank you all for that. I suppose I disagree a bit that the only sane route to go is the stock route. By going the stock route the bike will cost roughly $15,000 to repair and it is pristine except for the trailing arm, the front subframe and parts forward of those points. There's not even a scratch on the painted surfaces except for the front fender and of course one of the valve covers. It's a bit frustrating that perhaps 25% of the bike costs as much to repair as an entirely new bike.

If I rented an arc welder and fabricated a front subframe to hold a triple clamp and forks in an unproven geometry I would expect pretty bad results. However, such a conversion can be made to precisely replicate the OEM suspension geometry or another proven setup. Not only that but it can be done with parts that are adjustable to allow further finetuning of the setup.

The telelever is certainly a great setup. I love it. However, there are many great suspension setups that people who are not BMWophiles prefer and would never consider giving up for a telelever. Since I don't have the option of replacing the telelever setup except with a new bike and since it seems silly to total the bike I'm open to considering some other options.

[Sander Abernathy]

Seriously,
The formula for a well handling motorcycle has been developed over a century of engineering and on street experience and just increasing the tire size or changing the rake by a degree could have a major effect on how some bikes handle. Bikes like the one in the picture look cool but taking one out on the road and riding it hard (not putting around a parking lot like the builders usually show) might put a rider at risk. I'm not saying these modifications can't be done, but they should be done by someone that really knows what their doing not by some shade tree guy with a torch in his hand.

I agree. I would need to use a proven geometry and measure it to a fraction of a degree and the mm. That's what these guys are for:

http://www.gmdatl.com/index.htm

[mogu83]

It would be interesting to see what that company would charge to design, build and take the legal responsibility for what you propose. If you contact them please post their answer.

If your fixing your bike yourself E-bay, Beemer Boneyard, Bob's BMW and I'm sure other places usually sell good used parts for half of list. Good luck on the rebuild, it's quite a project.

[nylife]

http://cgi.ebay.com/ebaymotors/BMW-R120 ... ccessories

[tinytrains]

Given the bike has no steering head or bearings, this would be an onerous task. You have to design and install a conventional steering head. The ball joint at the top of the forks is just to keep them lined up. It can not carry the weight of the bike. The telelever does that. You would be designing your own motorcycle and trusting your life to it. How much do you know about chassis stability and resonance? Companies speed huge amounts of money running simulations and testing to get this right.

Just find used parts. I know it is hard to find them.

Scott

[dutchie]

I agree. Keep it original. It must have been close to a total. It scares me a little that the front is 2/3 the cost of the bike.

[Tarmac]

It's Friday nite, and I've had a couple beers, so don't quote me on this.

Go for it.

Don't listen to these ball-less geezers, you could have the coolest beemer ever! But it's gonna take a guy (not me), with a huge sack to make happen

You could get the entire front end from a gixxer for nothing, and the end result would be BAD ASS!!!

Just don't fall for the stupid, thigh burning, high pipe. Keep it low.

Get that duel head light set up from Buell ($115!!!), and some clip ons. May as well spring for a new paint job while your at it.

YOU CAN DO IT!!!!

[sweatmark]

This is quite do-able, and you have options:

1. That BMW LoRider concept bike appeared to employ the newly-developed (at that time) HP2 frame; note the unused mounting bosses. Not the option I would choose.

2. Right now via quick eBay search, there are several key pieces of the rebuild puzzle, including R1200 fork tube sliders ($175), an R1200S Telelever A-arm ($149 obo), and the aforementioned front shock unit. Rebuild using good secondhand parts is the simplest option. Might take some time to gather the needed items, but consider the task a significant-cost-savings scavenger hunt.

3. Rebuilding bike to use conventional forks is also possible, though this might be the first such attempt. Yes, the warnings about safety/stability concerns WRT changes in bike geometry and component strength are warranted, but this idea is plausible. Here's why:

(a) the Telelever ball joints at top and bottom define the bike's steering axis, and its these ball joints that transmit all front wheel reaction forces to the bike's front subframe. Under normal conditions, the Telelever steering axis changes slightly under compression of the front suspension, which shortens the distance between ball joints, and increases rake and trail relative to the front subframe. Compare this with conventional forks, where the steering axis is defined by steering tube, and both rake and trail decrease under fork compression.

(b) Telelever upper and lower fork mounts differ from conventional triple tree pieces because fork tube position is maintained by (top) mounting bolts set in flexible seats to hold sliders; and (bottom) the built-in step at side of fork tubes locks the bottom clamp in place. Conventional triple tree uppers and lowers require stronger structure because the only thing holding the fork tubes in place is clamping force; it's exactly for this reason that adjustment of front end geometry is possible for conventional forks by sliding fork tubes up or down within the triple tree.

(c) normal Telelever forks do nothing but maintain linkage integrity via unrestricted sliding motion; the front shock of the Telelever linkage transmits the front wheel's z-direction reaction force (bike mass) up into front subframe, and the A-arm transmits longitudinal reaction force back into the engine cases at the A-arm mount bearings. Now imagine that you magically move the front shock's damping and spring forces into the fork tubes... this is akin to installing conventional "sprung" forks internals into the empty Telelever forks. You could still use the A-arm to maintain the steering axis via lower ball joint, but such would require a solid strut as replacement for the normal Telelever front shock unit. The upper ball joint and front subframe would still function as before to define the steering axis. The lower ball joint would remain fixed relative to the upper ball joint, as would the A-arm. And the old Telelever linkage attachment points on front subframe and engine cases would still transmit the same reaction forces as before.

(d) the final engineering would require that you fabricate or modify conventional triple tree upper and lower to accept the Telelever ball joints, and you would need to shop carefully for a conventional "sprung" front end (forks and triple tree clamps) whose overall dimensions was a very close match to the original Telelever fork tube assembly. Matching the original linkage geometry would be crucial for preservation of front end stability, allowing that you would thus have a bike that loses some portion of rake and trail under fork compression, similar all bikes with conventional forks.

Shopping list for creative option 3:

Conventional forks/front end, including triple tree (top and bottom clamps);
Solid strut to replaceOE front shock unit, preferably with some length adjustment via tie rod threaded ball ends;
Brakes (if originals cannot be reused);
Wheel (if original cannot be resused);
Front axle (if original cannot be reused);
Handlebar mounts, if not already incorporated into triple top;
Mount piece to hang OE instrument/headlight module.

[mogu83]

Don't listen to these ball-less geezers, you could have the coolest beemer ever! But it's gonna take a guy (not me), with a huge sack to make happen.
You could get the entire front end from a gixxer for nothing, and the end result would be BAD ASS!!!
Just don't fall for the stupid, thigh burning, high pipe. Keep it low.
Get that duel head light set up from Buell ($115!!!), and some clip ons. May as well spring for a new paint job while your at it.
YOU CAN DO IT!!!!

VERY NICE - OBVIOUSLY SOMEONE WITH YEARS OF EXPERENCE BUILDING BIKES.

[boxermoose]

Look to the HP2 for inspiration - wonder if the front end would bolt up

[snag]

If you're looking to save $$$ and not build some "bad a$$" custom, a conventional front ended R1200R is probably going to go cheap at resale. Ask yourself: would you buy one?

Doug

[deilenberger]

2. Right now via quick eBay search, there are several key pieces of the rebuild puzzle, including R1200 fork tube sliders ($175), an R1200S Telelever A-arm ($149 obo), and the aforementioned front shock unit. Rebuild using good secondhand parts is the simplest option. Might take some time to gather the needed items, but consider the task a significant-cost-savings scavenger hunt.

Problem is - this is a 2011 bike, and the front end changed with the intro of the 2011 models - so parts that fit off eBay are going to be very scarce for quite a while. The older front end parts might fit - if you can buy everything that bolts up to the subframe and engine.. otherwise, no promises (and I'd guess they just won't fit..)

A bit of snipping..

(c) normal Telelever forks do nothing but maintain linkage integrity via unrestricted sliding motion; the front shock of the Telelever linkage transmits the front wheel's z-direction reaction force (bike mass) up into front subframe, and the A-arm transmits longitudinal reaction force back into the engine cases at the A-arm mount bearings. Now imagine that you magically move the front shock's damping and spring forces into the fork tubes... this is akin to installing conventional "sprung" forks internals into the empty Telelever forks. You could still use the A-arm to maintain the steering axis via lower ball joint, but such would require a solid strut as replacement for the normal Telelever front shock unit.

You'd have no compression at all if you used a solid strut in place of the telelever shock.. the telelever shock/strut is the easy part of the problem - many of us have barely used ones laying around gathering dust since we went to aftermarket suspension. I have two of them actually - and would donate one to Sander if he could use it.

I think the practicality of engineering your own front end is somewhat daunting, and in the end will cost at least what buying parts and rebuilding it with stock parts will. Custom machining, quality welding and precision tubing fabrication don't come cheap.

One thought that is interesting - is how would the HP2 stuff fit? Problem again that I can see is the front subframe - since all the electronic stuff mounts to it under the tank.. but the mounting points to the engine are likely there and unused or used for something else, so it wouldn't be necessary to engineer the front end itself (and you'd have one that was designed to be safe by people who know what they're doing.) Since the HP2 has been out for a while - there are likely some that have been stuffed somehow and parts available from them. Big problem with the whole project - the most likely damaged parts in almost any crash are the front end parts (left-turners are the biggest cause of totals..) so the parts that aren't damaged are hard to find and come at a high price.

Be interesting to see how this turns out..