Is it safe to straighten bent forks? - CBR Forum - Enthusiast forums for Honda CBR Owners

Is it safe to straighten bent forks?

  #1  
Old 10-31-2018, 12:09 PM
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Default Is it safe to straighten bent forks?

Hi fellow riders and greetings from Greece. Got a '09 CBR 600RR. Long story short, should i straighten bent forks or buy a new pair?

I had a car crash on my left side(about 50km/h) after he steered right without noticing me and among other damage forks are slightly bent, but without any leaks or visible damage.(my mechanic told me after he took them off and inspected) . Going to take them to a suspension specialist in the next days so he tells me if and in what degree they are bent and my mechanic told me that this guy can probably straighten them.
Anyone ever done this or knows more on this?How risky it is to go for a fix?Should i pay the extra buck and go for brand new to be safe? I dont want to trust a suspension guy because he might just want my money and doesnt care about my safety. A brand new costs alot and i have to pay some extra on top of insurance money which is alot for me at this moment.
Having in mind i ride quite fast when on this bike and i want to feel and be safe will doing it. Also its a bike i want to keep for the next 2-3 years.

Ride safe everyone and i hope someone has some feedback


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  #2  
Old 10-31-2018, 05:30 PM
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If it were me, I'd probably replace the tubes. It's a few hundred bucks, but if you're paying a mechanic to do it, that'll probably end up costing almost as much

Curious how someone would straighten one of these. You could tie it down and pull it, but you'd probably have a really tough time getting it perfectly round again, and if you overpull it it'd just kink right up. It's not like you could get a dolly on it. My guess is he'd tie the bike down and use a ratcheting strap to pull onto the front wheel while tapping around the damaged area. Even with a good repair you'd get fatigued metal where the bend used to be, which is a bit sketchy. It might make it more susceptible to future failures, especially if you took a similar bump in the future

Would it get you on the road? Probably

Is it worth saving a buck or two? Your call
 
  #3  
Old 11-03-2018, 08:50 PM
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There ARE places here in the US that straighten forks (http://www.framestraightsystem.com/M...0%20Repair.htm), but it's a job for a pro...it's not a DIY project.
 

Last edited by EchoWars; 11-03-2018 at 08:53 PM.
  #4  
Old 11-07-2018, 11:14 PM
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I doubt they're actually bent. More likely they are twisted in the clamps.
Loosen the lower clamps.
Straighten the front wheel.
Have a friend hold the wheel in the straight position.
Turn the bars to straight riding position.
Tighten the lower clamps.
Take it for a ride slowly increasing speed.
Report back in with findings.

Welcome to the forum George!
 
  #5  
Old 12-21-2018, 07:35 AM
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Timbuctwo's suggestion is certainly the first thing to try, and that could very well fix the problem. It could also be that the steering stem is bent, a distinct possibility since modern, upside-down forks are extremely strong and are likely to transmit the force of a crash further into the bike.

As for your original question, yes it's possible to straighten forks and I've done it, however it was on old-timey rightside-up forks. It was common practice in the old days and is even covered in some older factory manuals. On those bikes, though the forks bent at the lower triple clamp, well away from the sliders meaning that the repair didn't have to be abolutely perfect to work. On an upside-down fork the bend will affect the inner tube's passage into the outer and must be dead-accurate to work.

The procedure for straightening involves completely disassembling the fork and laying the bent tube in a pair of V-blocks. A dial indicator on a stand Is set up and the tube rolled over in the V-blocks to find the high side. This is repeated along the length of the tube until the highest point of the bend is found and marked with a sharpie. This entire procedure should take place on a machined flat surface, the top of a table saw being adequate for the job.
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An attempt is then made to bend the tube back into shape (I used to use wooden blocks and a vise). You'll have to bend the fork past the desired position to get it straight. Then it's back to the V-blocks, repeating the entire procedure until straightness is achieved.

Before attempting this you should know:
- A pro would check the tube between centers, as on a lathe
- A pro would straighten the fork in a press, allowing much more accurate force to be applied
- You could try this and be unable to staighten the fork
- You could try this, believe the fork to be straight and reassemble the fork only to have it bind when compressed, meaning the repair was a failure.

In my opinion the best way to correct a modern, bent fork is to replace the bent tube with a known-good part. This could be new, used, or your original part professionally straightened.
​​​​​​
​​​
 

Last edited by Commander_Chaos; 12-22-2018 at 08:20 PM.
  #6  
Old 12-21-2018, 04:19 PM
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TimBucTwo’s suggestion would be my first course of action. If the forks were proved to be out then I’d do my best to prove the source of a second hand pair before committing.
Straightend will surely never truly be as strong as original and that’s where repairing falls short.
Best of luck mate and glad you didn’t get injured.
 
  #7  
Old 12-31-2018, 03:25 PM
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Found this in a book about restoring old Brit bikes. I will absolutely try this if provided with the opportunity.
 
  #8  
Old 01-01-2019, 02:50 PM
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Originally Posted by Commander_Chaos View Post

Found this in a book about restoring old Brit bikes. I will absolutely try this if provided with the opportunity.

Hah. That looks super sketchy.
 
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