Frame bracing

[Yamavarna]

I need some tips on bracing my frame. I have searched a lot and can’t seem to find what I am looking for; there doesn’t seem to be a simple effective frame bracing post. I’m thinking a few plates at the steering head, some gussets around the swingarm pivot and shock mounts, maybe a tube or 2 on the lower cradle, just enough to help with my new suspension, tires and brakes. This forum has been a blueprint of information for my new build and once again I need your help!

[brrrappp]

Frame bracing is more of an art than a science.
If you have monitored racing tech both MX and Street over the years, then you know that some frame flex is desirable.
Too much flex and the bike is wobbly too little and it tends to have an unpredictable traction limit causing high-sides.

I haven't heard much about RZ frames cracking or breaking from the stress created with wider/stickier tires.
If you are looking for increased lap-times and frame flex is holding you back, look to see what the fast guys are doing at the track.
Welding up braces where it "looks good" will most likely create unintended problems elsewhere.

[Yamavarna]

I did find some pictures on a site (east coast rz’s),
I also have some memories of bracing up Kz’s and GS’ from back in the day (helping to build Superbikes for the Canadian series) so with a little common sense and having read Tony Foale’s book I think I am going to just wing it

[silverstrom]

Talk to smoker about what he did with his frame Charlie. He has a very long thread and if you go through it you'll find some useful info. The link takes you to the end (pg 156). I have no idea where the frame bracing starts.

Happy hunting! viewtopic.php?f=5&t=2499&p=169983&hilit ... ng#p169983

[giron]

frame bracing on a RZ350 frame? The RZ350 frame is the Achilles tendon of the RZ350. Why not try a delta box frame. A VJ21A or a RZ250 aluminum frame.

[giron]

frame bracing on a RZ350 frame? The RZ350 frame is the Achilles tendon of the RZ350. Why not try a delta box frame. A VJ21A or a RS250 aluminum frame.

[MK]

In your other thread you stated it'll be a road bike.

Frame bracing is used on 70's scrap to make it half way rideable/reliable or on 80's scrap to get the last 10'th of a second out of your laptime.
None of that applies to a road RZ with a standard rider on top.

Only remaining motivation is posing like "look, how cool that guy modified his frame".
But that'd only be cool back in the 80's when there weren't aluminum framed GP replica bikes all around.
Nowadays it's just pathetic, being more like "poor chap, couldn't afford the 3MA frame"

Seriously: I ride my road RZ since 1987 for some 235.000km and I do race my other RZ at a level of around 10% over lap record on my home track (which is fast for hobby riders).
I never felt I'd need a frame brace - neither for durability nor for speed. That one thing that cured the wobbly suspension was a modern fork/swingarm plus 17 inch wheels & proper sport tires.

Actually I'm a mechanical engineer and even work in the field of numerical simulation. Years ago I let the sim chew up some additional tubing on the RZ frame, but the stiffness increase especially in torsional stiffness wasn't really worth the effort.

[Yamavarna]

In your other thread you stated it'll be a road bike.

Frame bracing is used on 70's scrap to make it half way rideable/reliable or on 80's scrap to get the last 10'th of a second out of your laptime.
None of that applies to a road RZ with a standard rider on top.

Only remaining motivation is posing like "look, how cool that guy modified his frame".
But that'd only be cool back in the 80's when there weren't aluminum framed GP replica bikes all around.
Nowadays it's just pathetic, being more like "poor chap, couldn't afford the 3MA frame"

Seriously: I ride my road RZ since 1987 for some 235.000km and I do race my other RZ at a level of around 10% over lap record on my home track (which is fast for hobby riders).
I never felt I'd need a frame brace - neither for durability nor for speed. That one thing that cured the wobbly suspension was a modern fork/swingarm plus 17 inch wheels & proper sport tires.

Actually I'm a mechanical engineer and even work in the field of numerical simulation. Years ago I let the sim chew up some additional tubing on the RZ frame, but the stiffness increase especially in torsional stiffness wasn't really worth the effort.

I’m not a mechanical engineer but I have raced most of my life and can definitely tell the difference between a stock and a braced frame, my last race bike was a 2003 gsxr and I did a ton of work to get that thing to turn although it was very stable, I still have a fireblade race bike and it works well after a lot of suspension work. Both of the aluminum framed bikes are head and tails better at being hustled around a track than any of my 80’s steel framed bikes. And, the memories of trying to manhandle the stock 80’s bikes around the backroads while the front and back wheels where visually bouncing out of line is harrowing now, compare that to hustling my r1m around those same roads and it feels like a Cadillac. I understand that the rz is lighter and already has a perimeter frame but adding the additional forces of modern suspension, brakes and rubber is going beyond what that frame was engineered for, a mechanical engineer should understand that.

[giron]

I have a 1990 RZ350. It handle well, but what an improvement with 17" wheels 3X17 in the front and 4.5X17 in the rear with soft compound tires. The frame didn't complain

[Yamavarna]

I’ll take this into account but I have to do some more research before it goes to Powdercoat

[RuZty]

Racing slicks and about double the power of a tuned RZ350, tell me the frame doesn't look familiar;



It probably uses better tubing than a production bike, but I doubt that frame is any way near twice as stiff as an RZ frame. Maybe the RZ was over designed.

My RZ has all the usual power mods, inverted forks and an RGV swingarm. I never considered bracing the frame and have never found the bike lacking enough to bother. I'm not saying it won't help a bit, but I bet a very talented rider would get far more out of some suspension tuning than any frame bracing. Don't feel like it's something you have to do, I think the returns on a street bike are extremely limited. If you can do it yourself and want the experience knock your socks off, but if you just stiffen one area you are sending the forces farther down the line. If you can't measure where it's the weakest how can you hope to improve it?

[Yamavarna]

3 of my friends had that bike back in the day and even with skinny bias ply tires they where flexy flyers, but, they did have at least twice the horsepower. One of them (my best friend) 2 time Canadian Superbike champion Art Robbins (god rest his soul) did have a local welder (Paul Young) brace the frame and he noticed an immediate improvement; I remember the exact braces that he put in and it was very small triangle gussets around the swingarm pivot and a small plate on both sides of the steering head, if I remember correctly it was a 4340 alloy frame, so... I think at the very least I will copy what Paul Young did back in the day, grind off all of the unnecessary mounts then call it done and it will be off to the Powdercoaters (which is a weekly run for me this year anyway). I appreciate all of the input and rest assured I will not be building a replica Ducati frame on of this build but some subtle well placed gussets in a stock appearing street bike with some modern suspension, brakes and rubber. I do however need some input on the grade of steel to use; I’m thinking .125” 1018 what do you all think? That’s about it for this thread it’s on to wiring next Motagadget m-unit blue and Zeeltronics PDVI-11VT

[brrrappp]

While you've got her stripped down and shaved clean, check the weld around the side stand mount. I've seen two RZ's where the side stand mount started to tear away from the frame. It's the only weak spot I have ever heard about.

[MK]

The RZ frame is a standard steel comparable to St37.
It can be welded with standard SG-2 rods.

0.02$ on comparing to aluminum frames and race bikes:
Late 80's and early 90's aluminum frames were incredibly weak as they basically tried to re-do the steel version in aluminum (like the RZV500 or the NS400R or early GSXR's). In addition they often had quality issues in welding and tolerances.
In 1993 I spoke to an Audi colleague who was in charge for the aluminum space frame of the first A8. He said they brought all major Japanese big bikes and cut the frames in order to learn how to do this for cars.
The result did not match the automotive OEM quality criteria because most of the Japanese welds would have failed a German quality audit.
So NATURALLY welding these things up does improve the chassis and you'd even notice that on the road.

Comparing it to a race frame is a different thing. The wall thickness in the RZ is thicker than in an according TZ.
That's the reason why there're lighter than the road bike.
(we're talking about something like a 1.7mm compared to 1.3 mm, both standard steels, early TZ did not use CrMo tubing)
As a side effect these race frames cracked from time to time at junctions and so they benefit from minor bracing to distribute the loads to a bigger area of material.

On the non PV RD350LC's the bracing is half way sensible as this frame is not optimal. The UK guys do that all day long, especially when converting to 100+ hp cylinders.

[Yellow and Black RZ]

When you feel like she's going to buck you off loosen your grip and ride it out. Easier said than done.