SERPENT 120
04-27-2009, 03:10 PM
#751
Well I got the S120 front suspension mounted on my BMI and tested it out this weekend. I found this front end by far has the least amount of bind in it when assembled of the 3 front ends I have tried so far (Stock AE, CRC, and Serpent). For less then the cost of the CRC with the long upper arm conversion (at least when I bought it) this kit comes ready to be assembled in 2 lengths of upper arm. The upper arms have 0 bind in them. The only bind I found was the typical tight lower pivot ball. All in all it is a really beautiful kit...but I do have a few gripes.
The first is that it comes with no instructions at all. It really isn't a difficult suspension to build but instructions with tips would have been nice. I downloaded the full car's instruction manual for the front end just to make sure I was doing things right. One of my threaded inserts had some buggered threads. I didn't have a tap but fortunately I had the steel 8-32 screw that comes with the IRS arms and I used that to repair the threads. Earlier I said the upper arms had 0 bind...well there is good reason for that, the upper arms actually have a bit of slop in the mount. This can be remedied easily with some very thin shims. Also, the kit comes with a 6 degree upper arm mount, 3 and 9 degree mounts are also available but not included with the kit. I would have preferred the kit come with the 9 degree mount as that would have put it much closer to the 10 degree most of us use in 1/12th. To buy a 9 degree mount is going to cost another $36...almost half the cost of the complete kit. I'm not liking the flat spots for the wrench on the king pin. I will probably be replacing these with the CRC ones and pivot ball even if I don't bend them. The placement of the pivot ball in the arm is a bit higher then in the IRS or CRC arm, so there is less adjustment for ride height. This can be particularly irritating on outdoor asphalt tracks where ride height tends to be a bit higher. Due to this I was unable to use my BMI spacers in the front for ride height adjustment. The kit does come with some really nice machined ride height shims in 2mm, 1mm, and .5mm...but they are made for the size screw the S120 uses to mount the front end on and are slotted too small for a 8-32 screw. I also found that the screw for the pivot slop adjustment and the threading on the axles are not long enough to engage the nylon part of the lock nut. I had a nut fall off the pivot screw in the middle of the race. Fortunately right now the pivot ball is still really tight in the arm and I don't really need the screw in. As for the axles I was using the older style Parma wheels and was nervous all day about the nut coming off. This next race I'll be using Jaco Prisms, hopefully they will be a bit more narrow across the bearings so more of the nut threads on. All these are fairly minor issues...but with the amount of thought that looks like went into this front end I would have expected these issues to have been worked through.
Now I have a couple of questions regarding the adjustments available on this front end. The first is with the cross brace...what effect is stiffening this going to have on the car's handling? The other is with the upper arm mounts...the instructions show a spacer that mounts under them to raise the mount. I assume this is a tuning aid and can be removed to mount the mounts lower. If I do what effect will that have on the handling of the car?
The first is that it comes with no instructions at all. It really isn't a difficult suspension to build but instructions with tips would have been nice. I downloaded the full car's instruction manual for the front end just to make sure I was doing things right. One of my threaded inserts had some buggered threads. I didn't have a tap but fortunately I had the steel 8-32 screw that comes with the IRS arms and I used that to repair the threads. Earlier I said the upper arms had 0 bind...well there is good reason for that, the upper arms actually have a bit of slop in the mount. This can be remedied easily with some very thin shims. Also, the kit comes with a 6 degree upper arm mount, 3 and 9 degree mounts are also available but not included with the kit. I would have preferred the kit come with the 9 degree mount as that would have put it much closer to the 10 degree most of us use in 1/12th. To buy a 9 degree mount is going to cost another $36...almost half the cost of the complete kit. I'm not liking the flat spots for the wrench on the king pin. I will probably be replacing these with the CRC ones and pivot ball even if I don't bend them. The placement of the pivot ball in the arm is a bit higher then in the IRS or CRC arm, so there is less adjustment for ride height. This can be particularly irritating on outdoor asphalt tracks where ride height tends to be a bit higher. Due to this I was unable to use my BMI spacers in the front for ride height adjustment. The kit does come with some really nice machined ride height shims in 2mm, 1mm, and .5mm...but they are made for the size screw the S120 uses to mount the front end on and are slotted too small for a 8-32 screw. I also found that the screw for the pivot slop adjustment and the threading on the axles are not long enough to engage the nylon part of the lock nut. I had a nut fall off the pivot screw in the middle of the race. Fortunately right now the pivot ball is still really tight in the arm and I don't really need the screw in. As for the axles I was using the older style Parma wheels and was nervous all day about the nut coming off. This next race I'll be using Jaco Prisms, hopefully they will be a bit more narrow across the bearings so more of the nut threads on. All these are fairly minor issues...but with the amount of thought that looks like went into this front end I would have expected these issues to have been worked through.
Now I have a couple of questions regarding the adjustments available on this front end. The first is with the cross brace...what effect is stiffening this going to have on the car's handling? The other is with the upper arm mounts...the instructions show a spacer that mounts under them to raise the mount. I assume this is a tuning aid and can be removed to mount the mounts lower. If I do what effect will that have on the handling of the car?
04-28-2009, 02:22 AM
#752
Went home tonight after posting and tried with the Jaco Prism wheels and I am running into the same issue with the front axle not being long enough for the wheel nut to engage the nylon...how is everyone working around this? I was running the nut backwards but one of them started acting up and won't thread on properly this way any longer.
04-28-2009, 05:01 AM
#753
Went home tonight after posting and tried with the Jaco Prism wheels and I am running into the same issue with the front axle not being long enough for the wheel nut to engage the nylon...how is everyone working around this? I was running the nut backwards but one of them started acting up and won't thread on properly this way any longer.
04-28-2009, 06:15 AM
#754
Went home tonight after posting and tried with the Jaco Prism wheels and I am running into the same issue with the front axle not being long enough for the wheel nut to engage the nylon...how is everyone working around this? I was running the nut backwards but one of them started acting up and won't thread on properly this way any longer.
i found the wheel nuts supplied with the scalpel (1/18 pan car) work well.
04-28-2009, 11:13 AM
#755
Thanks guys...I will look for the low profile nuts. I just hope Serpent takes heed and looks into this for future customers. It's the 3mm one right?
04-28-2009, 02:09 PM
#757
Cool thanks
04-28-2009, 08:36 PM
#759
Unfortunately very few of the new generation of wheels can use a non-flanged bearing. The Jaco Prism, Parma (Jaco Prism in black), and the CRC all use a flanged bearing.
05-01-2009, 02:55 PM
#760
I found a solution to my axle nut problem 
Rather then ordering a bulk pack of low profile nuts of which I will only use 2...or paying for shipping on just 2 nuts from somewhere else. I found a 3mm tap at a local harware shop and tapped out a 4-40 aluminum lock nut. Fits perfectly and holds quite well
Rather then ordering a bulk pack of low profile nuts of which I will only use 2...or paying for shipping on just 2 nuts from somewhere else. I found a 3mm tap at a local harware shop and tapped out a 4-40 aluminum lock nut. Fits perfectly and holds quite well
05-03-2009, 10:14 AM
#763
Hello Pete:
First , welcome to 1/12.
Second, that is NOT a slipper clutch, that is a ball diff. You should tight it up until you can not move either tire while holding at the same time one tire and the spur. Instead of going from full tight to loose, go from loose until you tight it correctly. Do it in small increments, until you can hardly move or slip.
First , welcome to 1/12.
Second, that is NOT a slipper clutch, that is a ball diff. You should tight it up until you can not move either tire while holding at the same time one tire and the spur. Instead of going from full tight to loose, go from loose until you tight it correctly. Do it in small increments, until you can hardly move or slip.
Also it appears that there is 2 different axle threaded parts - 1 has 3 ridges and the other is threaded both of them are different lengths of thread?
A CRC Axle should work in this as a backup? Nothing more fun than loading the car up and getting to spend your day waiting for loctite to dry.
05-03-2009, 11:13 AM
#764
I just use an IRS axle and hubs, since I wasn't thrilled with the quality of the OEM axle.
05-03-2009, 11:35 AM
#765
