Vtec Rebound Adjustable Forks.

[Guest v4bluey]

I wanted to upgrade my forks as I was not happy with the ride or handling. I don't mind the linked brakes and I wanted to keep the bike as standard as possible parts wise. I have previously changed the rear shock to a F4i which prooved a valuable asset to the handling and ride.

I am 145lb/66kg the vtec forks were sh1t for me. Harsh on bumps and all over the place on bumpy corners and under heavy braking on rough surfaces. I tried using 5w oil but the low speed orifices were too large and the ride became mushy on slow damping. I'm not an aggressive rider and we have sh1t roads round here.

I purchased a set of .90 Sonic springs.

I also purchased a set of F4i forks thinking I would be able to use the cartridges, sadly they don't fit the vtec lowers. They have a larger outer diameter than vtec cartridges also the top out spring is in a different position.

What I did was use the F4i rebound adjustable caps and damper rods in the vtec cartridges. This gave me rebound adjustment. They are shorter rods but I was still able to get it together with the spring spacer size for my weight.

I then chamfored all shim and refill orifices in the f4i valves (same valves as the vtec with different shim arrangement) I didn't change the orifice size just chamfored.

I then changed the standard compression stack from 17,17,16,16 x .1 to 17, 16, 16, 15 x .1 (i wanted a little less compression damping) If you are an aggressive rider I would probably leave the other 17x.1 shim in.

I changed the rebound stack from standard 17,16,15 x.1 to 17, 16, 15, 14 x .1 a bit extra damping for the heavier springs.

The next thing was the oil, I used a 50/50 blend of Motul Expert 5w and 10w to get 7.5w. this oil has a similar viscosity rating as the standard Honda oil.

I used a lower level of oil in the forks. 525cc's instead of 545cc's.

I set the rebound to one turn and the rider sag to around 35mm, at that the static sag was 20mm which is reasonable. The rear is around 32 to 33mm.

I was after smooth, progressive damping and I must say it seems quite smooth now. I have not had a chance to set it up yet and have only been for one 190 kl ride to test it. This ride was over a rough track and I had no problems with steering and the ride was 100% better. It was raining so I didn't get a chance to push the bike.

I have to fit new rubber soon and then dial it in and give it a full test to see what else it may need. I am very happy with the outcome at this stage and i'm sure it can be made better.

Edited February 19, 2008 by v4bluey

[Baileyrock]

Great job, many have done this same mod(F4/F4i) internal in the vtec and F3 internals in the 5th gen to get the Rebound dampening. It's suppose to be the best adjustment to have if you only have one! :thumbsup:

[Guest v4bluey]

Thanks Bailey,

This modification came about because of the information I gleaned from members of this forum like yourself, HS, Turtle and others.

Thanks also to the advice and website of Peter Verdone, a very valuable place to get a speedy understanding of the inner workings of suspension.

Blue.

[Guest v4bluey]

BTW this post was also a warning to others who may purchase an entire set of F4i forks thinking the cartridges will drop in.

I paid $330 AUD for the used pair of forks delivered and the tubes were slightly bent, I knew this when I purchased them. I may heve been able to purchase just the items I needed for less.

The vtec cartridges are thinner wall steel units and the F4i are thicker wall aluminimum units. They are a little different in the top out spring position and possibly other measurements but I didn't bother to take measurements, sorry.