swapping triples out with less offset in triples - handling effects?

[Chuck78]

If I were to swap out my 77-79 gs750 triple clamp setup with an 80-82 gs750e with less offset, I know I will be decreasing my trail. How/how much is this going to affect my handling? I am looking at various 185mm width triples in varying offsets. Here is what I have noted in offsets:

77-79 gs750b/c/n most offset 175mm wide
GR650 same offset 195mm wide
83 gs750e w/16" front wheel & monoshock slightly less offset by 1/4" from memory
80-82 gs750e less offset than 83
Various L models & some 1100E leading axle fork models - least offset off all, lower triples that look like a rectangular block vs a V

 

[Chuck78]

If a slight bit less offset will still provide excellent stability at higher speeds & make for a quicker turn in, then I think the 185 width83 gs750 is the ticket. I've been browsing eBay for straight leg fork 80-82 gs750 base model triples for photos showing offset, but not much luck thus far.

Should I be keeping as close to stock offset as possible, or is a slight offset reduction along with all the suspension/tire/wheel mods in my signature going to update my handling/geometry more towards modern standards for sporty bikes?

With a 110/90-18, my tire is so close to the fork lower legs that I can't fit a fender, & I randomly got a 1980+ gs750/etc (35mm fork leg 185mm spacing) ATK fork brace, so I am wanting to swap on a wider triple for better clearance & being able to fit a fender again.

 

[GregT]

You've got it the wrong way round - less off set equals MORE trail, slower steering, more steering effort.
More off set equals LESS trail, quicker steering, less effort.

 

[Chuck78]

Ahhhh darnit! I got it backwards in my head from not fully visualizing the effects!

Sooooo... If I got the 83 GS750 triples, I would have slightly less offset & slightly more trail, which would allow me to raise the rear slightly, not hurting my ground clearance, & steepen my rake to quicken steering. What would the ill effects of this move be?
I was getting a slight bit of headshake between 42-55mph that went away after 55&up. I had 3/8" shorter forks up front with same triples as stock. Now I have gotten gs750 fork inner/upper tubes to stick in these GS650 lowers, so that will raise the front end back up again, and I also got AllBalls needle bearing conversion bearings for the steering stem. Both of these should improve things, but I want this bike to really corner well but not sacrifice in stability in the 40-100mph range, or even the odd 125mph day if I ever do any track days.

I was thinking this 83 GS750 triple with slightly less offset is going to be the ticket. Looking at some vintage race bikes, I noticed that they had billet machined triples with less offset than stock (considerably), but I didn't notice what they had done in terms of possible front/rear ride height stance changes.

 

[GregT]

A lot of vintage racebikes are on 17inch wheels so most seem to set the frames up from scratch. Usually steeper head angle which means that in order to get the required trail, less offset is needed.
FWIW our GS1000 racebike has an unmodified head angle, std length fork tubes,Std triple clamps, 17 inch wheels and longer shocks. Result is around 25.5 degrees rake and 96 - 97 mm of trail...and very good handling indeed.

 

[limeex2]

A lot of vintage racebikes are on 17inch wheels so most seem to set the frames up from scratch. Usually steeper head angle which means that in order to get the required trail, less offset is needed.
FWIW our GS1000 racebike has an unmodified head angle, std length fork tubes,Std triple clamps, 17 inch wheels and longer shocks. Result is around 25.5 degrees rake and 96 - 97 mm of trail...and very good handling indeed.

GregT, What model bike do you use for your 17 inch wheel set up? What about brakes, ect? What shock length?

 

[bluezuki]

I am confused.......I thought that less offset equals more trail which equals quicker steering/less effort. At least that's what I have found on my "other" bike which is a 77 Kawasaki KZ 1000 (notorious for heavy pig-like handling) where I swapped out the triples for a KZ 650 setup (1/2" or so less offset) and the result is a much better behaved sweet handling bike, and it still looks stock!!!

 

[John Kat]

I am confused.......I thought that less offset equals more trail which equals quicker steering/less effort. At least that's what I have found on my "other" bike which is a 77 Kawasaki KZ 1000 (notorious for heavy pig-like handling) where I swapped out the triples for a KZ 650 setup (1/2" or so less offset) and the result is a much better behaved sweet handling bike, and it still looks stock!!!

Sorry but it's the contrary: more trail equals slower and heavier steering.
Just look at the specs of modern bikes and you will see that the trail has decreased a lot over the years.
For the same reason bikes with a 17" front wheel are far easier to turn than those equipped with an 18" or worse a 19" wheel, all other parameters beeing equal.

 

[bluezuki]

Thank you, I'll have to figure out how/why the geometry on my bike actually works!!

 

[GregT]

GregT, What model bike do you use for your 17 inch wheel set up? What about brakes, ect? What shock length?

Wheels are Suzuki 3.5in front,4.5in rear, same as most from '88 onwards. Brakes are Brembo 08 calipers front on 296mm discs on home made solid carriers - we can now go bigger and float them but see no need as this works very well. Rear is the disc which came with the wheel and the OE GS1000 caliper on an underslung fully floating home made carrier. Again, works very well. Shocks are Gazi with the lightest springs available for them. Bike's at the owner's place so can't give you the shock length but they're the longest Gazi list for the GS from memory.
Actually, going bigger on the front discs would mean changing to probably Lockheed calipers...The Brembo's are a "tall" caliper and there's effectively zero clearance caliper to rim. Lockheeds are somewhat lower profile - but a lot dearer...