Will Reducing unsprung front wheel weight reduce handlebar vibrations?

[BertRemington]

Will reducing unsprung wheel weight improve comfort?

I'm the third owner of a 2014 RT-S SE6 with 12-spoke wheels (tastefully painted by a PO in rattle-can flat black); new Vredestein Quatrac 5 | 165/60R15 tires; and new Ikon 7613-1006 shocks.

The Vredesteins weigh 12lbs with 4 tread plies, two of which are steel, and one sidewall ply. They are sturdy. I run them at 18psi.

The Ikons are great. Very compliant with minimal if any stiction and Heim bushings on both ends to eliminate rotating friction. I love them. I run them at the minimum rebound setting.

I wear uninsulated deerskin/elkskin gauntlets and have Grip Puppies on my handlebar ends.

I want to reduce the shock to my hands from hitting the variations from smooth that characterize much of our San Diego roads.

My thinking is to reduce unsprung wheel weight by changing to PPA wheels (https://www.slingmods.com/can-am-spyder-widow-series-front-rims-ppa-wheels or https://www.slingmods.com/can-am-spyder-orb-series-front-rims-ppa-wheels, whichever is lighter) and Can-Am 165/55R 15 (p/n 706202317) tires (5.6lbs, plies unknown but I'm sure they are more compliant than Vredestein).

Tomorrow I'll ask SlingMods about the weight of the PPA wheels but I'm sure they will be less than the BRP 12-spoke wheels.

I have two questions:

1) will this combination of reduced wheel weight, reduced tire weight and increased tire tread/sidewall compliance will reduce shock to my hands?

2) are there alternatives to this combination?

Thanks.

 

[Peter Aawen]

There's a chance that changing the rims to lighter rims might help reduce the vibrations you feel at the handlebars Bert, but I really don't think going back to CanAm tires (Kendas) will help at all, and in fact, due to the higher pressure they need to run at in order to let them operate safely, thereby REDUCING the benefits of their lighter sidewalls & total weight, they'll more likely detract a LOT from overall suspension compliance! :lecturef_smilie: Then add in their known poor quality control record, meaning that it's pretty much a crap shoot that you'll get a set of tires that run smoothly at the best of times, :shocked: there's a good chance they might even make those shocks/vibrations transferred up the line & into your hands WORSE, even with everything else you've done bringing improvements!! :gaah:

You say you've got Grip Puppies on the handlebars - are those the grip cover type foam grips, or are they the bar end-weights that are designed to reduce grip vibrations?? If the former, then you should really look at adding the latter too . Adding a set of those end-weights to your bars as well as running the softer grips might do the trick! And if you keep the Vredestein tires, but fit them onto a set of (lighter) PPA rims, and maybe try running them at 16 psi instead of 18 psi, you should be well on the way to doing just about everything you can in order to reduce any shocks/vibrations being passed into your hands! hyea:

Besides running quality tires (like the Vredesteins) at an appropriate pressure on quality lighter rims; making sure the shocks/coils are in good condition & not set too hard; running end-weights on the handlebars; and fitting vibration absobring type foam grips to the bars; the only other thing that I've ever tried that had any real benefit in reducing hand shock/vibrations was wearing gloves with impact/vibration absorbing thin gel pads in their palms, the web between thumb & forefinger, & under the first bit of each finger... but I haven't seen any gloves like that for some years now... you might still find them over your way, but while a few oldies here remember them as working very well, no-one local here in Oz seems to stock them anymore! :dontknow:

Over to you! Good Luck! :cheers:

 

[Eckhard]

I am not a tire expert but consider the following.

Vredstiens mentioned above are rated for 905 lbs max load per tire.
Kenda Kanine, a Spyer tire, is rated at 485 lbs load per tire.

Logic would dictate that a tire that is designed for a max 3600 lbs car and is mounted on a 1300lbs Spyder + driver combo will give a harsher ride, even with reduced tire pressure, than the OEM tires.

 

[PMK]

Front shocks need a bit less LSC and somewhat more reduction in HSC. Not sure what IFP pressure, if more than 10 bar, reduce to 10 bar also. You might need a slight increase in spring preload if IFP pressure is reduced more than 3 bar.

Expecting compliance and control by reducing unsprung weight alone will have minimal good results. My opinion, the shocks are valved too firm.

 

[BertRemington]

PMK -- thanks. I'll ask Ikon if the valving can be changed.

 

[BertRemington]

Peter -- the comfort issue isn't vibration, it's shock. When I drive over one of those reflective bumps in lane dividers, I want the gentlest reminder rather than a thump. There's probably a limited range of correction due to the high laydown angle of the front shocks.

WRT tires, the Vredesteins start off heavier and stiffer. If you look at tires as an air spring, it's rising rate but for the small transitions I'm interested in (ie reflective bumps) that's I think pressure is less a factor than tire weight and sidewall stiffness. So I still have an open mind on the BRP tires.

WRT Grip Puppies, they are a foam handgrip. I also have add-on bar end weights. Vibration isn't an issue.

Many of my motorcycles were kinda shy on cylinders so I'm familiar with gel/vibration-damping gloves but never used them. I was younger then.

Thinking about PMK's suggestions, I'm going to increase spring height adjustment (the Ikon shock has about 1 inch more travel and spring length than the BRP). Maybe I'm not in the sweet spot of shock operation. That also might explain why I'm getting understeer from the Vredesteins.

Thanks all for suggestions.

 

[Peter Aawen]

Peter -- the comfort issue isn't vibration, it's shock. When I drive over one of those reflective bumps in lane dividers, I want the gentlest reminder rather than a thump. There's probably a limited range of correction due to the high laydown angle of the front shocks.

WRT tires, the Vredesteins start off heavier and stiffer. If you look at tires as an air spring, it's rising rate but for the small transitions I'm interested in (ie reflective bumps) that's I think pressure is less a factor than tire weight and sidewall stiffness. So I still have an open mind on the BRP tires.

WRT Grip Puppies, they are a foam handgrip. I also have add-on bar end weights. Vibration isn't an issue.

Many of my motorcycles were kinda shy on cylinders so I'm familiar with gel/vibration-damping gloves but never used them. I was younger then.

Thinking about PMK's suggestions, I'm going to increase spring height adjustment (the Ikon shock has about 1 inch more travel and spring length than the BRP). Maybe I'm not in the sweet spot of shock operation. That also might explain why I'm getting understeer from the Vredesteins.

Thanks all for suggestions.

As I said, there is only a chance that the lighter unsprung weight might make a difference to the transmitted shocks (AND to any vibrations passed up too ), but I'm not at all convinced that it'd be a big difference. However, besides the testing I've done myself, quite a few companies & other people who are well respected in the tire industry have done a LOT of testing/modelling on varying tire pressures & the impact (Ha!! Didja catch that pun? ) that pressure change can make on the ride (& handling et al ) and I think you'd be surprised at HOW MUCH difference even just a couple of psi can make to your suspension compliance/ride comfort with the sort of impacts you mentioned! Trying to describe this at it's simplest, it's not really the bag you put it in, but rather it's pretty much the air inside the tire (or bag ) that carries the load of your vehicle & works as part of the suspension, and unless you've chosen a tire that's capable of carrying WELL OVER the load imposed upon it by your Spyder & you/your load etc (ie. +10 x's, not just 3 x's ) just about anybody will likely notice the difference made by varying the pressure inside the bag/tire by as much as 2 psi out of 18.... :thumbup:

You can test this for yourself if you like - just get yourself a lightweight party ballon & similar sized but much heavier duty display balloon, and inflate them both to the same pressure, enough to about 1/2 inflate the lightweight balloon should be ample - unless you've gone for a pressure that's already perilously close to exploding the party balloon, such that it does explode when you press it with or against anything or press it up against & then try to slide it along any surface (ie, higher pressure, more risk of puncture/catastrophic failure due to hitting road debris! ) then you'll likely find that not only does the proportionally less inflated heavy balloon not explode and provide more traction to resist that slide, but it feels 'softer' when pressed up against anything because it's not as close to it's maximum pressure capacity as the more lightly constructed party balloon is! :shocked: . Similarly, the stronger tire sidewalls on most car tires over OE Spec Kendas work in much the same way - if you inflated the heavier tires to the same pressure as that required by the OE tires to let the lighter constructed tire carry the load (a load that's very close to its max load) then what you & Eckhard surmise would apply; but if you only inflate the heavier built tire to the lesser pressure necessary for IT to carry the 'significantly lighter than its max load' load, it should be AT LEAST 'as soft a ride' as the OE tire running at it's much higher pressure - and if you drop the heavier tire a couple more psi, then it's going to give you a proportionally softer ride. :thumbup: However, there is a point of diminishing returns, and if you go low enough, it actually starts making things worse rather than better - altho for most of us running auto tires under their Spyders, that pressure is down below about 14 psi, so you're not there yet!! :lecturef_smilie:

You could certainly try varying the settings you've currently got on your shocks & springs, within the range that's possible on them now you're running Ikons, but I wonder if you'd be better served by changing the angle the shock assy works on?? :dontknow: Blueknight911 made some upper shock mount adaptors (I think Pitbull did a version of them for early Spyders too?!?) that pushed the top of the shock out away from the centerline of the frame so that the shock assy was operating at an angle a little closer to vertical, and even with the OE shocks that made a fairly significant improvement on their operation, including ironing out some of the 'shock' you'd feel at the handle bars by hitting a pot hole!! :dontknow:

Over to you! :cheers:

 

[PMK]

Thinking about PMK's suggestions, I'm going to increase spring height adjustment (the Ikon shock has about 1 inch more travel and spring length than the BRP). Maybe I'm not in the sweet spot of shock operation.

The front suspension design is primitive. With the Spyder loaded with 3/4 fuel, typical junk in the trunks, and riders verify ride height. There is no true sweet spot as on a real rising rate setup.

Adding travel via longer stroke dampers is not a great idea. Using any increased travel, assuming current ride height is close, will hinder handling.

Increased damper stroke allows greater chassis roll prior to unweighting an inside tire. On a performance vehicle, especially with three wheels, added chassis roll, at speed can upset the chassis dramatically. A 1970s Honda ATC is a viable example.

In simple terms, based on my over 40 years of suspension tuning, including revalving gas DeCarbon type dampers, you simply feel harshness on account of poorly valved suspension. The dampers are hydraulically preventing the wheel / tire to correctly follow the ground.

Unless you are loading the Spyder to nearly fully hitting the bottoming cushions, the spring is dumb and can react entirely as needed.

You already have the rebound freebleed clicker fully open. This also reduces LSC on account of LSC flow through the rebound freebleed, unless they use a check nut or TT design. Regardless, anytime a clicker is maxed out, it is a very good indicator the valving is incorrect. When you have the shocks sent in for revalve, they should also soften rebound, rebound LSR possibly even rebound HSR. In a very extreme case of poorly setup / valved dampers, your suspension is packing and failing to extend adequately for the next bump.

As mentioned, unless you are riding with enough load to compress the dampers onto the bottoming cushions, your dampers need some attention to a correct internal shim settings change. All the best with it.

BTW, if the shop starts saying words about using a shock dyno, ask them what the dynos capability of in inches per second is. Most buy 20 IPS units which is great for riding on a pool table or bowling alley. 60 IPS or more will give ok data to take out the harshness you feel. My guess is they will shim shuffle some new settings, charge for a rebuild and cross their fingers, but maybe not.

 

[Rednaxs60]

Going to follow. Look forward to how you resolve the issue.

 

[BLUEKNIGHT911]

As others here have posted ..... you are searching for PERFECTION and you will not find it for a Spyder .... Even folks who own very high end Luxury veh's have many complaints...... So, ride more - worry less ..... JMHO .... Mike :thumbup: