Twins vs. Mono

[focus frenzy]

shocks smocks!!!!! the biggest gain in performance and handling is getting rid of the cast lead stock wheels!!!!

the monster wide rear wheel and tire on my SV weighs less than the front tire and wheel on my 1000G. that right there is all unsprung weight.

with a mono shock set up weight transfer to the chassis from the wheel remains the same, straight up the middle. with dual shocks it moves to either side through the shock on the inside of the turn.

you have to be realy realy good and fast to tell or benifit from the change but many gain just from the stiffer swing arm as the older steel swingarm was pretty flexy. the later boxed aluminum one is stiffer.

look at our Australian katana friends, in the pictures Dink has posted many of them are running modern ultra light alloy spoked wheels.

 

[reddirtrider]

with a mono shock set up weight transfer to the chassis from the wheel remains the same, straight up the middle. with dual shocks it moves to either side through the shock on the inside of the turn.

I must differ on this. Both shocks in a dual setup work in a corner. The only way one shock will have an advantage is if there is significant flexibility in the swingwarm or through the frame connections. I've even seen production bikes with a single shock setup on one side of the swingarm. There is no transfer back and forth in a properly designed system.

The biggest advantage of a mono over a duel seems to be in setting up the suspension. You have a greater range of tuning and you only have to do it for one shock, not both.

In a production environment, anytime you can eliminate components, especially costly one such as a shock, manufacturers are going to go for it.

Take for example our tube frames. They can be made strong enough, take Ducati for instance, but they are much more expensive than the monique units. So, manufactures go that route.

 

[drhach]

Mono shocks sure do impress the ladies though.

 

[80GS1000]

redirtrider is speaking from experience. He did one of the nicest builds you'll ever see.

redirtrider - do you have any pics of your bike? Would love to see it.

 

[reddirtrider]

redirtrider - do you have any pics of your bike? Would love to see it.

I built it for my son and it's not accessible right now. I used to have a thread on it here, but it's probably been deleted.

I'm going to be working on it again after I get the 750ES rebuilt. I'm going to either rework the mono bracing to go with more of a Ducati look (tubular) or convert back to a dual setup and use modern shocks.

There's plenty of examples in here and you have a beautiful bike. Nice job. I really like what you've done.

 

[Billy Ricks]

I built it for my son and it's not accessible right now. I used to have a thread on it here, but it's probably been deleted.

I'm going to be working on it again after I get the 750ES rebuilt. I'm going to either rework the mono bracing to go with more of a Ducati look (tubular) or convert back to a dual setup and use modern shocks.

There's plenty of examples in here and you have a beautiful bike. Nice job. I really like what you've done.

The old thread is probably in the archives but the pics would be dead. Might be able to find it through Katman's thread.
Found a link in Katman's thread and yours is dead.
http://www.thegsresources.com/_forum/showpost.php?p=272001&postcount=44

 

[Guest]

On my GS1100 I've got the dual shock set up on a bandit swing arm with GSXR tires, its certainly better than stock.

There may be someone on the site who has ridden both mods (dual vs mono) but I doubt it. I have mono on my 01 FZ1 and love it. There are too many other variables to compare one to the other from bike to bike and the same is true on GS conversions. How good of a job did the builder do, what combination and quality of components were used.

I think you just have to decide what "Vision" you have for how you want your bike to look. The ride quality and performance will be governed by your skills and your components.

 

[liloaty]

I must differ on this. Both shocks in a dual setup work in a corner. The only way one shock will have an advantage is if there is significant flexibility in the swingwarm or through the frame connections. I've even seen production bikes with a single shock setup on one side of the swingarm. There is no transfer back and forth in a properly designed system.

I agree that both shocks work in a corner, but they will not be under the same load. Properly designed systems can reduce this, but not totally eliminate it.

 

[reddirtrider]

I agree that both shocks work in a corner, but they will not be under the same load. Properly designed systems can reduce this, but not totally eliminate it.

If your swingarm and chassis mounting points are sufficient stiff, where would the differnt loads come from?

The only difference I can see at that point is the individual responses of each shock. Good quality shocks should be very close to each other tolerance wise.

In any case, what you'd have is an averaged system contolled by the responses of each shock. If the swingarm and chassis are sufficiently stiff, you wouldn't even need a shock on each side. A mono mounted on only one side of the rear would work (if it was the correct shock for the application).

 

[liloaty]

If your swingarm and chassis mounting points are sufficient stiff, where would the differnt loads come from?

Nothing is infinitely stiff, and in a turn the bike + rider's center of gravity will be different distances away from each shock and its mounting points.

 

[reddirtrider]

Nothing is infinitely stiff, and in a turn the bike + rider's center of gravity will be different distances away from each shock and its mounting points.

Somehow I just don't see how a swingarm that doesn't meet the infinitely stiff test will flex with a shock on each side and affect the handling dynamics, yet if it flexes with a mono it won't.

 

[liloaty]

Somehow I just don't see how a swingarm that doesn't meet the infinitely stiff test will flex with a shock on each side and affect the handling dynamics, yet if it flexes with a mono it won't.

Well, first off the mono swingarms are much stiffer than that dual shock swingarms. Second, even if the swingarm with a monoshock flexes, the shock is still putting its reactive force on 1 point on the frame. With 2 differing reactive forces, like in a dual shock setup, it can cause the frame to twist.

 

[reddirtrider]

Well, first off the mono swingarms are much stiffer than that dual shock swingarms. Second, even if the swingarm with a monoshock flexes, the shock is still putting its reactive force on 1 point on the frame. With 2 differing reactive forces, like in a dual shock setup, it can cause the frame to twist.

Ah, one of the pre-requisites to this discussion was that the mono swingarm and the dual shock swingarm are equally stiff. That's a very simple task, just use a mono swingarm for both applications.

As for the frame, once again the assumption is that it's stiff enough. If that's the case (and it's entirely possible) there is little difference as far as the geometries of the relationship between the wheels and frame.

The mono will always be easier to tune, but I just how a well designed dual setup is inferior.

 

[liloaty]

Ah, one of the pre-requisites to this discussion was that the mono swingarm and the dual shock swingarm are equally stiff. That's a very simple task, just use a mono swingarm for both applications.

As for the frame, once again the assumption is that it's stiff enough. If that's the case (and it's entirely possible) there is little difference as far as the geometries of the relationship between the wheels and frame.

The mono will always be easier to tune, but I just how a well designed dual setup is inferior.

OK - I'll give you the equally stiff swingarm assumption, but the frame assumption I don't agree with.

If frames were "stiff enough" then Suzuki, Honda, Kaw, Yamaha, Ducati etc etc wouldn't be pouring money into frame R&D like they do. I don't think its fair at all to say that a frame, for this argument, is infinitely stiff or stiff enough not to be twisted by unequal shock loads.

 

[reddirtrider]

OK - I'll give you the equally stiff swingarm assumption, but the frame assumption I don't agree with.

If frames were "stiff enough" then Suzuki, Honda, Kaw, Yamaha, Ducati etc etc wouldn't be pouring money into frame R&D like they do. I don't think its fair at all to say that a frame, for this argument, is infinitely stiff or stiff enough not to be twisted by unequal shock loads.

I'm not saying the mono isn't better, it's just I believe you can build dual shock units that virtually none of us could distinguish from a mono. That's my standard - that virtually none of us could tell the difference. (I'd say none, but I may be underestimating someone)

 

[tone]

Having done a few mono conversions on gs's etc here's my thoughts .......

A stock gs twin shock steel swingarm is lighter than something like a bandit 12 ally arm but no where near as stiff

Once you add the linkages etc there is a significant weight penalty but its gained back when you add the rest of the components, wheels tyres disc brakes etc & most of this is unsprung weight which can only be a good thing

The main advantage of mono arms is the rising rate linkage, twin shocks or cantilever mono shocks can never compare for quality of ride & keping the tyre in contact with the road

Twin shocks put the forces generated into two top mounting points that where never strong or stiff when new & after 20 or 30 years of use WILL be misaligned even if they were straight from the factory which is doubtfull at best

Ive had brand new unused frames on the jig that had the mounts up to 5mm out of horizontal with a 3 to 5mm differance in distance from the centreline of the frame, All of this puts strain on the stock rather weak swingarm & no matter what shocks you use they will be working at slightly differant damping rates because of it

Monoshock conversions when done properly put the forces generated directly into the strongest part of the main frame, above the swingarm pivot & up below the tank area, a little bracing here works wonders for handling

tone

 

[reddirtrider]

Having done a few mono conversions on gs's etc here's my thoughts .......

A stock gs twin shock steel swingarm is lighter than something like a bandit 12 ally arm but no where near as stiff

Once you add the linkages etc there is a significant weight penalty but its gained back when you add the rest of the components, wheels tyres disc brakes etc & most of this is unsprung weight which can only be a good thing

The main advantage of mono arms is the rising rate linkage, twin shocks or cantilever mono shocks can never compare for quality of ride & keping the tyre in contact with the road

Twin shocks put the forces generated into two top mounting points that where never strong or stiff when new & after 20 or 30 years of use WILL be misaligned even if they were straight from the factory which is doubtfull at best

Ive had brand new unused frames on the jig that had the mounts up to 5mm out of horizontal with a 3 to 5mm differance in distance from the centreline of the frame, All of this puts strain on the stock rather weak swingarm & no matter what shocks you use they will be working at slightly differant damping rates because of it

Monoshock conversions when done properly put the forces generated directly into the strongest part of the main frame, above the swingarm pivot & up below the tank area, a little bracing here works wonders for handling

tone

All true, but you're comparing a properly built mono to a stock setup. Use a good swingarm with the associated brakes and wheels, brace and align the frame, use quality shocks and it's an entirely different story.

Yes, the mono is easier to tune, and the rising rate linkage is great, but if you do all of this work to a GS to convert it to a mono, you have to be fair and do the same to upgrade to a decent twin shock setup.

I would be great to have the Yoshi bike with modern wheels and tires on a track next to a converted mono so we could compare them.

 

[tone]

All true, but you're comparing a properly built mono to a stock setup. Use a good swingarm with the associated brakes and wheels, brace and align the frame, use quality shocks and it's an entirely different story.

Yes, the mono is easier to tune, and the rising rate linkage is great, but if you do all of this work to a GS to convert it to a mono, you have to be fair and do the same to upgrade to a decent twin shock setup.

I would be great to have the Yoshi bike with modern wheels and tires on a track next to a converted mono so we could compare them.

True i'm comparing a mono conversion to a stock twin shock setup to a small degree, using a better/stiffer swingarm with twin shocks will show an improvement but the fact remains the top mounts are still pretty poor & that is where the problems lie plus you still end up with no proper rising rate

Putting a monoshocked gs & an upgraded twinshock head to head on the track is pointless as tracks are reasonably smooth & there will be little differance if any but try it on the road with all its potholes, off camber corners etc & its a different story

 

[LilTinc]

Putting a monoshocked gs & an upgraded twinshock head to head on the track is pointless as tracks are reasonably smooth & there will be little differance if any but try it on the road with all its potholes, off camber corners etc & its a different story

Tone,
Are you saying you think the mono set up would work better over real road type conditions or that the "twin vs. mono test" should be performed on real roads instead of a more uniform close course track surface?

 

[Mark M]

The main advantage of mono arms is the rising rate linkage, twin shocks or cantilever mono shocks can never compare for quality of ride & keping the tyre in contact with the road

The advantages of rising rate are greatly exaggerated for road and track use. Current sport bikes and MotoGP bikes use very little rising rate, less than 10% for the most part. That can be achieved with twin shocks that are moderately inclined forward a bit. I don't know where the GS models lie as I have never measured one out. Rising rate is excellent for dealing with load variations, but is a tuning problem if you are trying for really good track performance.

One of the biggest advantages is that it is hard to find top quality twin damper sets and it is easy to find very good single dampers. Even the premium Ohlins twin units are only middling grade compared to the high end mono units.

Mark