Recently I have completed the modification of 17" rims; the front is FZR1000 (1988) with FJ1200 (1992) forks + RPM spring/vales , back GSXR1100 (1992), and the riding characteristics have completely changed. I am not sure if I love the change. The bike is more "lazy" to turn, keeping upright. I am interested with quickening the steering however. Is there any way to "quicken" the steering? I do not wish to go back to 16".
The front tire is a 120/70ZR17 (58W) CONTI ROAD ATTACK 2 GT
Thanks,
Eyal
Sounds like you forgot to raise the rear end.
That goes hand in hand with what you have already done and will quicken the steering response greatly.
Leon
Leon,
How do I raise the back? I forgot to mention that on the back I replaced the shock with RPM's shock.
Eyal
What year do you have?
If you have dog bones, then shorten them.
If older, I bow to owners of same with advice.
Leon
Leon,
My FJ1100 is 1985; no dog bones on the bike.
Eyal
effectively,what you did was,at this point,is to raise the front and lower the rear...which,as you found out will slow the steering...probably,substantially. The 17" front,now taller (vs. the 16") and the rear 18" tire is actually shorter that your typical 150/16 rear, by just a little. That said...im pretty sure your only option is a taller rear shock...Penske makes one,Randy at RPM may be albe come up with something as well. That last piece of the puzzle is what you are looking for...it will transform your handling into what you intended. hope this helps.
Quote from: eeshed on August 22, 2013, 01:25:21 PM
Leon,
My FJ1100 is 1985; no dog bones on the bike.
Eyal
Not yet that is...
Let's review shall we? No..No...No..The difference
is not with your new front 120/70-17 tire.
Tire Size Comparison
Specification Sidewall Radius Diameter Circumference Revs/Mile Difference
120/80-16 3.8in 11.8in 23.6in 74.0in 856 0.0%
120/70-17 3.3in 11.8in 23.6in 74.2in 854 0.2%
Your new 180/55-17 rear tire is the culprit (good call Leon)
Tire Size Comparison
Specification Sidewall Radius Diameter Circumference Revs/Mile Difference
150/80-16 4.7in 12.7in 25.4in 79.9in 792 0.0%
180/55-17 3.9in 12.4in 24.8in 77.9in 813 -2.6%
You new 180 tire is about 1/2" smaller in diameter than your oem donut. Allowing for tread wear figure 3/4"
A couple of things you can do;
1. Lower the front end by:
a) Raising the stanchion tubes up in the triple clamps. Caution here: Fork dive....the RPM IAT valves uses softer fork springs than conventional cartridges or cartridge emulators, so beware of banging your fork brace on your fairing bottom, or horn. If you were using heavier springs, like a .95kg/mm or 1.0kg/mm springs I would say, go for it, give it a try....but I am unsure with the softer springs.
b) Installing a smaller diameter front tire. A 120/60-17 (with a shorter sidewall) will fit just fine on your 3.5" wide front rim and is almost 1" shorter than your existing 120/70 tire.
Tire Size Comparison
Specification Sidewall Radius Diameter Circumference Revs/Mile Difference
120/70-17 3.3in 11.8in 23.6in 74.2in 854 0.0%
120/60-17 2.8in 11.3in 22.7in 71.2in 890 -4.0%
c) any combination of a) and b) above
2. Raise the back end by converting your '85's swing arm linkage over to the '89/90 linkage which uses dogbones. I did this on my '84 and it wasn't that hard to do. The hardest part was finding the "relay arm" off a '89/90 FJ. The lower shock eye mount used on your '85 has to be swapped with a clevis style mount to fit the relay arm..(Randy @ RPM can help you there) Everything bolted up just fine on my '84. I used Soupy's adjustable dogbones so I could dial in the length exactly were I liked it.
Sorry for your disappointment, but no worries, we help get you there.
You made the right move by switching over to modern 17" tires (you know that right?) Now let's just dial it in
Keep the faith....Cheers. Pat
Quote from: eeshed on August 22, 2013, 01:25:21 PM
Leon,
My FJ1100 is 1985; no dog bones on the bike.
Eyal
You have 2 options, hope and wait till the adjustable RPM shock comes out, it should be a bolt on to your existing RPM shock. Or, convert over to dog bones. You wil need an FJ 89' shock link, shortened bones and the other bits as well. I will be doing this on my 86' as soon as I can afford the RPM shock.
Can't he just drop the yokes further down the fork tubes? AKA LOWER the front... Is there a functional limitation to doing this that makes it unattractive/ impossible?
Just a thought.
Dan
Edit: Ignore this, just saw Pat's comprehensive response to this that discusses this in much more detail.
You didn't by any chance, while you were working on the front end, adjust (tighten)the stem nut on your steering stem did you? A overly tight stem nut will have the effect on the steering that you are describing.
Eyal,
Give me a call. I have the answer(s) but there are many questions to make sure everything is covered and going back & forth via the forum is not the way to address the issue.
You can post up your solution when you are done.
Randy - RPM
Thank you all. I will contact Randy.
BTW, didn't touch the steering nut.
Eyal
Going the f4i shock route will raise the rear an inch or more.
Jeff
Quote from: jscgdunn on August 22, 2013, 03:43:23 PM
Going the f4i shock route will raise the rear an inch or more.
Jeff
Why would anyone trade off the RPM shock for the F4 shock? Got to be a better way.
CraigO
I think the RPM shock is a great option and again thanks to Randy for putting it together.
That being said, there are other options that may fit other budgets.
Jeff
Quote from: craigo on August 22, 2013, 03:46:26 PM
Quote from: jscgdunn on August 22, 2013, 03:43:23 PM
Going the f4i shock route will raise the rear an inch or more.
Jeff
Why would anyone trade off the RPM shock for the F4 shock? Got to be a better way.
CraigO
It could be a solution for someone else with a similar mod but who hasn't sprung (no pun intended) for the RPM shock. All input is appreciated.
Quote from: Dan Filetti on August 22, 2013, 02:53:44 PM
Can't he just drop the yokes further down the fork tubes? AKA LOWER the front... Is there a functional limitation to doing this that makes it unattractive/ impossible?
Just to further address this issue. Lower the bike too much in the front and you'll be scraping parts realtively easily.
Quote from: craigo on August 22, 2013, 03:46:26 PM
Why would anyone trade off the RPM shock for the F4 shock? Got to be a better way.
CraigO
There is and it is being resolved.
It all comes down to the basics...
Randy - RPM
Quote from: eeshed on August 22, 2013, 12:26:24 PM
The front tire is a 120/70ZR17 (58W) CONTI ROAD ATTACK 2 GT
Thanks,
Eyal
Interestingly, one of the many things I like about the RA 2's is the front tyre profile IMPROVES turn in dramatically compared to Dunlops, Michelins etc
Noel
Id swap my f4i shock for one of rpm's any day,, but for what the honda shock is its 100% better than a crapped out oem shock,
I just did essentially the same mod on my 85' and was completely happy with the handling change. When we talk about the rake angle quickening the steering what it means is that the bike will respond to handlebar inputs more quickly and will require lower effort at the bars to initiate a turn. However it doesn't mean it will take less effort to hold the bike in the turn. In fact there should be no effort to hold the bike in the turn at all. My bike steers more slowly than it did with the 16" wheel but requires absolutely no effort once established in the turn. I'm running a new set of Conti sport touring tires, I think maybe your problem is related to the tires, either a mismatch front to rear or inflation. Low inflation has always caused the bike to want to stand up in the turn in my experience.
I want to thank everyone for their input, but as I stated yesterday;
Quote from: racerrad8 on August 22, 2013, 04:15:25 PM
It all comes down to the basics...
I will let Eyal reply once he has gotten it all sorted, he is working on it.
Randy - RPM
I can tell how squared-off my rear tire is based on how much effort I put into counter steering through corners. :biggrin:
I kind of went "Tim Allen" on mine. If raising it a little is good them more is better... Well it's actually to quick for me at its present stance. I crudely measured my fork angle with a digital table saw angle finder and it looked to be 25 - 25.5 degrees. I think I am on my 3 rd engineered set of dog bones.
After I get my bike back together I am going to adjust it to 26 degrees and evaluate it. At speed it was OK but when I put the binders on it would get real quick, probably contributed a small amount to a problem I had at the WCR.
The above is just my opinion and experience. You can make them steer quicker.................
George
Quote from: FJmonkey on August 23, 2013, 07:11:50 PM
I can tell how squared-off my rear tire is based on how much effort I put into counter steering through corners. :biggrin:
Are you saying you need input into the bars just to initiate the turn or for the duration of it as well?
Noel
I'm curious to see how this all turns out... I just made 17' mod to front,yet to drive it till Monday and have Gixxer rear almost ready to go,but I swapped rear tires to give me some extra time for mod so I'll be running 17 front and stock rear set up....
My next question to all this is am I now on the hunt for a 89 and up rear swingarm set up...Cause I got a line on a whole 89 FJ for 800$ I'll buy it and donor it and part out
Quote from: ribbert on August 24, 2013, 02:40:43 AM
Quote from: FJmonkey on August 23, 2013, 07:11:50 PM
I can tell how squared-off my rear tire is based on how much effort I put into counter steering through corners. :biggrin:
Are you saying you need input into the bars just to initiate the turn or for the duration of it as well?
Noel
For the duration as well, raising the rear should really help since I have done the 17" upgrade.
Quote from: FJmonkey on August 24, 2013, 12:32:55 PM
Quote from: ribbert on August 24, 2013, 02:40:43 AM
Quote from: FJmonkey on August 23, 2013, 07:11:50 PM
I can tell how squared-off my rear tire is based on how much effort I put into counter steering through corners. :biggrin:
Are you saying you need input into the bars just to initiate the turn or for the duration of it as well?
Noel
For the duration as well, raising the rear should really help since I have done the 17" upgrade.
I'm sure it will. I raised the back a bit, dropped the front a bit, put the right tyre on and with only the slightest lean of my upper body I can "think" the bike into a corner and the bars remain neutral throughout. Love it.
Noel
Dear community,
I want to give you an update:
The bike is on a jack at the moment. Randy is working with me about setting a baseline for rear sag and front pre-load. From the initial investigation, the air pressure in the rear tire was too low (30'sh actual vs 42 recommended.) I am going to measure the rear sag and adjust it to about 40mm. My front preload needs additional approx 3/4" spacer. Note that the front is modified with an 80km RPM spring + RPM valve, 5w oil, and the rear is with RPM's shock.
My action plan is as follows:
- Set proper preloads, front and back
- Set proper air pressure
- Test
- Evaluate options based on results
I will get back with results as soon as I have news.
Randy, your help is unbelievable and I thank you very much for taking the time for supporting me with phone calls, emails, and pictures, all with the purpose of enabling my modifications to work.
Eyal
I hope your coming to FJ Clinic @ Tigers...love to see all this
Low air pressure in the tires will make the bike handle like a truck. I check air pressure every week or before every ride.
IMHO 42psi is too hard for a 180/55-17 radial. I like mine at 38 for solo riding.
Tire pressure dictates your footprint. Higher pressure, smaller footprint especially on the shoulders.
The oem bias ply tires needed higher pressures due to heat buildup in the tire carcass, but radial tires run cooler so they can get away with slightly lower tire pressures (thus a larger footprint).
To each his own.
Quote from: Pat Conlon on August 25, 2013, 03:12:32 PM
IMHO 42psi is too hard...
Since the RPM shock uses the softer spring the tire pressure can be run closer to the manufactures recommended maximum pressures. This eliminate the tire acting as more of a spring than the means of adhesion to the roadway.
With every other aftermarket suspension set-up people run on the FJ, the springs are stiff and the tire becomes another suspension component. Plus, when you have stiff springs and the tire is too stiff you have slippage issues, so yes that tire pressure will be too much for your bike or anyone else running any other aftermarket shock other than the RPM shock.
Tire manufactures build their tires to the maximum pressure and the deflection of the sidewall & tread are rated at the pressure.
By running at the recommended pressure, especially with the heavy FJ you have less sidewall deflection and there will not be any tread distortion due to lower pressures.
By lowering the tire pressure you might increase the external area of the contact patch, but the middle usually deflects upward, away from the asphalt causing it to loose contact with the road; this is also call tread roll.
The other benefit of being able to run the appropriate pressures is that you will not longer see the cupping associated with low pressure and tire deflection.
12,000+ miles out of a set Michelin Pilot Road 2 tires, front & rear are being seen with guys using the RPM suspension components running higher air pressures.
So, based on the testing of the RPM suspension components with regard to shock valving, spring rates and tire pressures, the results of the tire pressure range closer to the manufactures recommended maximum range is the optimum performance for the system.
Air pressure is a tuning & personal feel setting, but we have to start with
the basics...But, one thing is for sure,
RPM (http://www.rpmracingca.com) is re-writing the rules when it comes to FJ suspension components and the affect on the bikes handling ability and tire wear which are unparalleled.
Randy -
RPM (http://www.rpmracingca.com)
Got to ride bike this morning....first impression....feels light very little imput to get it to turn,felt little uncomfortable in a short turn.. I'll learn more next time I take it out...Blue dot brakes....dam! they are awesome!!!
UPDATE....Now that I know what to expect from swap I pushed it a little and felt good...dry roads help too...lol