Instability on C5

[CMB]

Dan - I've come to the same conclusion. I'm on a G5 and it was wiggly at speed on the freeway. I swapped the front tire for a Dunlop K70 and it got better - now it's just twitchy. On asphalt it's dead steady at freeway speeds. My dealer wants to play with the preload to see if that makes any difference. Maybe it'll throw some weight to the front and help the bike ignore the grooves.

[prof_stack]

... especially since this topic has been pretty well explored and all the possibilities noted by the great fellows here on the board. Just tryin' to save the man a little RIDING TIME! ...

It's riding time I want to get, and be able to hit the freeway slab when needed.  But have ALL the possibilities been discussed?  I'm not sure, but am working at it.

  I agree with scotty and scooterbob, it sounds like the grooved pavement in this case. I get the same problem with my other bikes on the roads that have it. On much heavier bikes to. It's that finely, straight line textured concrete on highways, that sucks. I think they do it so water drains better on hilly highway sections, to prevent icing. Like scotty said, the obvious test would be on flat black top. Also prof mentioned his tire pressure was a little above the recommended setting, how much?

A little twitching I expected.  A big wobble I did not.  That quickly sucks the fun out of a ride, let me tell you.  The grooves are bad for skinny tires.  Could that be one reason for the recent photos of wider tires for the C5 that we saw on this forum?

Tire pressure?  Funny that - which of my 8 gauges is accurate?  The AccuGauge showed 26psi front.  The newer pencil gauge showed 22.  I will take them to the tire shop and ask them to check the gauges.  Then I'll know more.

[gashousegorilla]

It's riding time I want to get, and be able to hit the freeway slab when needed.  But have ALL the possibilities been discussed?  I'm not sure, but am working at it.

A little twitching I expected.  A big wobble I did not.  That quickly sucks the fun out of a ride, let me tell you.  The grooves are bad for skinny tires.  Could that be one reason for the recent photos of wider tires for the C5 that we saw on this forum?

Tire pressure?  Funny that - which of my 8 gauges is accurate?  The AccuGauge showed 26psi front.  The newer pencil gauge showed 22.  I will take them to the tire shop and ask them to check the gauges.  Then I'll know more.

Tire pressure funny?  No. Definitely not. prof, try running your tires at 18-22 front, 24-26 rear. You should see a marked improvement. The Avon road riders on your bike have a very stiff, low profile side wall, along with a very rounded tread pattern that damn near goes from rim edge to rim edge. Designed for quick cornering, as in city riding. By lowering your pressures, to what the book says, not the plate at the front of the bike, your increasing your contact patch, and adding some flex in those side walls, giving you better high speed stability.
 Do the pressures sound too low? Yes, but not on this bike. Light bike, stiff tires.Very good tires in my opinion.They are great handlers. Would wider tires with a higher side wall aspect ratio help with the high speed stuff? Probably. But the trade off would probably be handling.We have found, the people on this forum, scooterbob,and myself,from literally working and testing every aspect of this chassis , all summer and found the pressure listed above to be the best.
 Could the problem be somewhere else on your bike? Sure. loose swing arm pivot? rims not trued? loose neck bearing? Could be any number of things. BUT it sounds like tire pressure. Give it a shot, it's simple. And we put alot of leg work into it.

[prof_stack]

Tire pressure funny?  No. Definitely not. prof, try running your tires at 18-22 front, 24-26 rear. You should see a marked improvement. The Avon road riders on your bike have a very stiff, low profile side wall, along with a very rounded tread pattern that damn near goes from rim edge to rim edge. Designed for quick cornering, as in city riding. By lowering your pressures, to what the book says, not the plate at the front of the bike, your increasing your contact patch, and adding some flex in those side walls, giving you better high speed stability.
 Do the pressures sound too low? Yes, but not on this bike. Light bike, stiff tires.Very good tires in my opinion.They are great handlers. Would wider tires with a higher side wall aspect ratio help with the high speed stuff? Probably. But the trade off would probably be handling.We have found, the people on this forum, scooterbob,and myself,from literally working and testing every aspect of this chassis , all summer and found the pressure listed above to be the best.
 Could the problem be somewhere else on your bike? Sure. loose swing arm pivot? rims not trued? loose neck bearing? Could be any number of things. BUT it sounds like tire pressure. Give it a shot, it's simple. And we put alot of leg work into it.

Thanks!  Much appreciated.

[r80rt]

I've finally decided on 20psi front and 24 rear, It feels perfect for my 180lbs.

[Ice]

Pencil gauges are the least accurate and consistent pressure measuring device.
 Dial type or digital gauges are preferable.

 Try googleing what the track day boys and racers have to say on the subject of tire pressure gauges.

[prof_stack]

A quick data point on instability: 

Today I drove the car on the same grooved pavement on the interstate that I rode recently on the squirrelly C5. 

Well, darned if the car started getting a little squirrelly on that same stretch of road.  Dry pavement, too. 

So, I'll test the C5 later on another place where the road is not groovy.

[Eamon]

A quick data point on instability: 

Today I drove the car on the same grooved pavement on the interstate that I rode recently on the squirrelly C5. 

Well, darned if the car started getting a little squirrelly on that same stretch of road.  Dry pavement, too. 

So, I'll test the C5 later on another place where the road is not groovy.

Hi Norm,
Was this stretch on I-5?  I hit a stretch north of the U-district, but south of Northgate, where our car got quite squirrelly.  I like my grooviness to be in my music, not my pavement, thank you!

Eamon

[prof_stack]

Hi Norm,
Was this stretch on I-5?  I hit a stretch north of the U-district, but south of Northgate, where our car got quite squirrelly.  I like my grooviness to be in my music, not my pavement, thank you!
Eamon

BINGO!  You win the prize.  From 80th to 130th is where I've experienced the instability while zooming north on I-5.

Groovy, man!   

[bob bezin]

yep I 5..from canada to seattle my triumph was squirrling all over the road i wondered what was wrong. took the ferry to port towndsend  and went down the coast a while then to corvalis got back on I5 and it was much better (not squirrily) on the way to ashland Or. yes that northern part of I5 was the worst part of a 5,518 mile trip

[iron.head]

Visited the best RE owned Workshop in my city. It was very nicely equipped with abundance of spares. The mechanics were also competent enough. One of the mechanics was working on the new TB500 and I asked him if the TB500 swing-arm would fit the C5. He said most certainly it will, but one can only come to know after giving it a try.

One of the specific features of the TB500 is the tubular swing arm which has specifically been designed to enhance stability of the bike after complaints of instability from the C5.

I plan to give the new swing-arm a try, but for that I will have to get it ordered for me and will be a waste if it doesn't fit my bike.

[Jack Leis]

What is a TB500 ? Have I missed something ?

[JVS]

Thunderbird 
http://royalenfield.com/motorcycles/thunderbird-500/

[Jack Leis]

Gotcha

[barenekd]

The I5 most any place has to be the worst road in the US.
Bare