Carbon fibre brake tie rod.

Bitza · 06-06-2020, 10:37 AM

OK all you technically minded people out there please tell me what you know. My dilemma is, I have a rear floating caliper arrangement aka 900ss superlight, M900Sie etc, and at present I use the standard Ducati aluminium (7075 or similar I guess) tie rod with male threaded rose joints + locknuts. However this lot weighs a ton, so some form of carbon fibre arrangement would seem the obvious way forward to shred a bit of weight. The most obvious way forward would be to attach one of the rose joints directly to one end and then have a coupling to the other to give a degree of adjustment at the other, but and its a crucial but how do you join metal joints to carbon effectively enough to take the braking force? would an external thread on carbon rod plus an adhesive be enough? Or perhaps use carbon tubing with an internal thread, which ever version it seems to me that the joint is going to be the weakest link. Another alternative would be to aim for a fixed length version with the rose joint part encapsulated in carbon so you would then be joining carbon to carbon. This idea is mainly to flex the old grey matter, while I go about shedding a few grams here & there but I'm running out of options. Bitza.

slob · 06-06-2020, 11:13 AM

any help?

http://carbonraceparts.com/Kart-Carb...25-KCFTRM8.htm

@285 mm max they look like they might be too short,

also I'm not sure about the stresses involved with kart steering as presumably the rods work as a pair and one is always in compression while the other is in tension.

the do make 'Ducati shift rods' and also seat struts for boats in custom lengths so it might be worth chatting with them, although they're obviously in US

also noticed they offer m10 in custom lengths http://carbonraceparts.com/Quad-Carb...FTR-length.htm

Darkness · 06-06-2020, 11:35 AM

I can’t see why you’d need to be able to change the length (Provided you get the right length in the first place), though it does need the rotational freedom at both ends to avoid locking the back suspension solid.
The rod is in tension when braking, so stiffness of the rod is unlikely to be a problem, but you need to be confident about how the rose joints are fixed to the rod? Just tapping a thread into the resin to screw the joint in is unlikely to work for long, if at all!
This could look really “trick” with the right engineering, but to save 100 grams, a short diet is likely to be more effective (And cheaper)!

Mr Gazza · 06-06-2020, 01:01 PM

I'm fairly sure that "Dirty" had a carbon torque rod on his 600. I think it came from America. I will try and do a search when I get a minute, unless someone beats me to it.
I don't know if he ever fitted it, he might still have it?

While the length is not hyper-critical, you definitely need a rose joint each end, besides it's the easiest way to create a tight swivelling joint. Those joints need to be kept in good nick too otherwise trouble follows. Use the Chrome-moly ones from McGills.

Having seen the way that carbon fails in model aeroplanes I don't think I would trust it myself for a critical structural part on a motorbike. The original is in fact an alloy tube so there is not very much weight to be saved. All the weight is in the rose joints anyway which are an essential part of the equation. lighter ones will almost certainly wear quicker?

A Titanium rod/tube would probably be better?

Dukedesmo · 06-06-2020, 01:02 PM

I recall reading that carbon fibre brake rods, whilst strong enough are prone to snapping if you use the rear brake if the bike rolls backwards (pushing rather than pulling), for example on a hill start etc.?

IMO it's one of those areas where a few grams saved is probably not worth the effort/hassle...

350TSS · 06-06-2020, 02:53 PM

Titanium is heavier than aluminium so a backward step, making a titanium one. Also, titanium tube is bloody difficult to get hold of and very expensive.
Personally I would not use a CF one as if it breaks (or the spherical bearing pulls out of the resin tube) when the brakes are applied (and I can see no reason why it would break unless the brakes are applied) the caliper will swing round the wheel spindle and smash into the top of the swinging arm, damaging it and the brake pipes. Any misalignment on the wheel spindle bearing will probably also cause the wheel to lock. With the brake pipe probably kinked the brake will not come off regardless of what your foot is telling the brake to do.

Mr Gazza · 06-06-2020, 03:46 PM

I searched for Dirty's torque rod but only found mention of it being fitted by Max some time after the infamous tunnel run.

I do recall that it looked exactly like the ones that Slob has linked to and I think he did have it custom made. They do say they will make any length if specified at checkout, so probably worth at least an email?

Dirty's had a threaded insert bonded into each end like those illustrated. I have no idea how he got on with it as he didn't do many miles after it was fitted and he has since sold the bike, presumably with the rod still fitted.

Grumpy would still have contact details for him if you wanted to ask him about it.

Pedro · 06-06-2020, 08:14 PM

Ducati used to fit carbon rods on some of the 888 SP Series bikes if memory serves correctly - pretty sure Natty had one for the kit I sold him. Pretty much in the hens teeth category for availability though.

From memory again I think there was a stainless steel threaded insert each end for the rose joints that was bonded in during manufacturing.

Dirty · 07-06-2020, 05:12 PM

Quote:

Originally Posted by Mr Gazza

I searched for Dirty's torque rod but only found mention of it being fitted by Max some time after the infamous tunnel run.

I do recall that it looked exactly like the ones that Slob has linked to and I think he did have it custom made. They do say they will make any length if specified at checkout, so probably worth at least an email?

Dirty's had a threaded insert bonded into each end like those illustrated. I have no idea how he got on with it as he didn't do many miles after it was fitted and he has since sold the bike, presumably with the rod still fitted.

Grumpy would still have contact details for him if you wanted to ask him about it.

Yep yep and yep. Got it from Slobs link above. Chap was very helpful, may even still have the specs he used. Looked great and worked well. Being yellow it was the fastest Monster anyway but the carbon rod definately made it at least 3.6753% faster on looks alone.

06-06-2020, 10:37 AM	#1
Bitza Bronze Member Join Date: Jul 2006 Location: Poole Bike: M900ie Posts: 470	Carbon fibre brake tie rod. OK all you technically minded people out there please tell me what you know. My dilemma is, I have a rear floating caliper arrangement aka 900ss superlight, M900Sie etc, and at present I use the standard Ducati aluminium (7075 or similar I guess) tie rod with male threaded rose joints + locknuts. However this lot weighs a ton, so some form of carbon fibre arrangement would seem the obvious way forward to shred a bit of weight. The most obvious way forward would be to attach one of the rose joints directly to one end and then have a coupling to the other to give a degree of adjustment at the other, but and its a crucial but how do you join metal joints to carbon effectively enough to take the braking force? would an external thread on carbon rod plus an adhesive be enough? Or perhaps use carbon tubing with an internal thread, which ever version it seems to me that the joint is going to be the weakest link. Another alternative would be to aim for a fixed length version with the rose joint part encapsulated in carbon so you would then be joining carbon to carbon. This idea is mainly to flex the old grey matter, while I go about shedding a few grams here & there but I'm running out of options. Bitza. __________________ Bitza Last edited by Bitza; 06-06-2020 at 03:37 PM..

06-06-2020, 11:13 AM	#2
slob . Join Date: Jul 2003 Location: East London Bike: Multiple Monsters Posts: 9,710	any help? http://carbonraceparts.com/Kart-Carb...25-KCFTRM8.htm @285 mm max they look like they might be too short, also I'm not sure about the stresses involved with kart steering as presumably the rods work as a pair and one is always in compression while the other is in tension. the do make 'Ducati shift rods' and also seat struts for boats in custom lengths so it might be worth chatting with them, although they're obviously in US also noticed they offer m10 in custom lengths http://carbonraceparts.com/Quad-Carb...FTR-length.htm Last edited by slob; 06-06-2020 at 11:38 AM..

06-06-2020, 11:35 AM	#3
Darkness . Join Date: May 2007 Location: Stockbridge Bike: M900 Posts: 1,984	I can’t see why you’d need to be able to change the length (Provided you get the right length in the first place), though it does need the rotational freedom at both ends to avoid locking the back suspension solid. The rod is in tension when braking, so stiffness of the rod is unlikely to be a problem, but you need to be confident about how the rose joints are fixed to the rod? Just tapping a thread into the resin to screw the joint in is unlikely to work for long, if at all! This could look really “trick” with the right engineering, but to save 100 grams, a short diet is likely to be more effective (And cheaper)! __________________ Original and Best since 1993

06-06-2020, 01:01 PM	#4
Mr Gazza Lord of the Rings Join Date: May 2013 Location: Norwich Bike: M900sie Posts: 5,805	I'm fairly sure that "Dirty" had a carbon torque rod on his 600. I think it came from America. I will try and do a search when I get a minute, unless someone beats me to it. I don't know if he ever fitted it, he might still have it? While the length is not hyper-critical, you definitely need a rose joint each end, besides it's the easiest way to create a tight swivelling joint. Those joints need to be kept in good nick too otherwise trouble follows. Use the Chrome-moly ones from McGills. Having seen the way that carbon fails in model aeroplanes I don't think I would trust it myself for a critical structural part on a motorbike. The original is in fact an alloy tube so there is not very much weight to be saved. All the weight is in the rose joints anyway which are an essential part of the equation. lighter ones will almost certainly wear quicker? A Titanium rod/tube would probably be better? __________________

06-06-2020, 01:02 PM	#5
Dukedesmo Registered User Join Date: Sep 2010 Location: Leics Bike: M900 Posts: 2,842	I recall reading that carbon fibre brake rods, whilst strong enough are prone to snapping if you use the rear brake if the bike rolls backwards (pushing rather than pulling), for example on a hill start etc.? IMO it's one of those areas where a few grams saved is probably not worth the effort/hassle... __________________ M900, 916, LeMans II.

06-06-2020, 02:53 PM	#6
350TSS Too much time on my hands member Join Date: Jan 2013 Location: Shipbourne Bike: M900 Posts: 1,419	Titanium is heavier than aluminium so a backward step, making a titanium one. Also, titanium tube is bloody difficult to get hold of and very expensive. Personally I would not use a CF one as if it breaks (or the spherical bearing pulls out of the resin tube) when the brakes are applied (and I can see no reason why it would break unless the brakes are applied) the caliper will swing round the wheel spindle and smash into the top of the swinging arm, damaging it and the brake pipes. Any misalignment on the wheel spindle bearing will probably also cause the wheel to lock. With the brake pipe probably kinked the brake will not come off regardless of what your foot is telling the brake to do.

06-06-2020, 03:46 PM	#7
Mr Gazza Lord of the Rings Join Date: May 2013 Location: Norwich Bike: M900sie Posts: 5,805	I searched for Dirty's torque rod but only found mention of it being fitted by Max some time after the infamous tunnel run. I do recall that it looked exactly like the ones that Slob has linked to and I think he did have it custom made. They do say they will make any length if specified at checkout, so probably worth at least an email? Dirty's had a threaded insert bonded into each end like those illustrated. I have no idea how he got on with it as he didn't do many miles after it was fitted and he has since sold the bike, presumably with the rod still fitted. Grumpy would still have contact details for him if you wanted to ask him about it. __________________

06-06-2020, 08:14 PM	#8
Pedro Ciao, come stai? Join Date: Apr 2003 Location: Somewhere Bike: Multiple Monsters Posts: 4,157	Ducati used to fit carbon rods on some of the 888 SP Series bikes if memory serves correctly - pretty sure Natty had one for the kit I sold him. Pretty much in the hens teeth category for availability though. From memory again I think there was a stainless steel threaded insert each end for the rose joints that was bonded in during manufacturing. __________________ M900 - 1993! Monster 1200R!