Beat The Clock

[chrisf]

Re: 360 bobber/Brat new tires update

I wouldn't worry about tearing the threads, in this case the primary stress is in shear against the stem itself. I doubt it'd be an issue...breaking I mean.

However....I wouldn't ride that setup or one similar to it, above say 25mph. As Troy stated, the wheel's axle (and hence hte wheel as well) travels in a pretty drastic arc, so nearly every parameter of the front geometry will exist in a nearly constant state of flux. The wheelbase will change constantly depending on what you're doing....like....riding it. On the gas you'll notice a little lofting but nothing wacky....on the brakes that thing will stand up in the front like mad and could conceivably (more than likely) net you a case of un-savable tank slappers. Not only will the wheel base shorten considerably under braking, but as the axle travels rearward your trail (and wheelbase again)will change to the point that the front end could 'caster' like a shopping cart. That doesn't sound all that bad until you remember that the weight transfers forward when braking (or just decelerating)...think on that for a bit.
Now think about the last shopping cart you had with the eff'd up front wheels...shaking back and forth.........

Not good.

I would worry about the threads in that situation, but you're right in there is a higher likelihood of shearing the stem. Based on the type of bike Troy built, it's more of a cruiser. But like you, I would be concerned with the dynamic change in wheelbase through the arc. I mean, if he leans into a turn and hits a bump, the whole bike will get squirrely.

Troy:

Whatever you go with, I would call swagger and chat the design over with him. He knows his stuff. Also, the reason why the suspension felt soft in the front is the leverage ratio used. If you think of it like a teeter-totter, the front axle to the first pivot is the long part. The short part is the pivot to the damper pick-up point. There are a lot of factors such as the damper mounting angle that effect the overall wheelrate, but I won't geek out on your thread. Put it like this: with enough leverage, my six year old can lift any of the Biggest Loser contestants. That's why I'm saying the stem (and threads) are incredibly stressed.

Regardless, I'm sure you'll design a cool system. Let me know if you need my help welding anything. But honestly, I really like your bike the way it sits now. It's kinda like importing a Russian model and promptly taking her in for plastic surgery. Kinda screwing with perfection. Besides, it would have been easier to date someone from LA/Miami/Dallas

OK, dumb pontification over. Time to get to my paying job.

--Chris

 

[Docta Jones]

Re: 360 bobber/Brat new tires update

Ah, I see now. It looked like a solid weld at first glance...

 

[Swagger]

Re: 360 bobber/Brat new tires update

It's kinda like importing a Russian model and promptly taking her in for plastic surgery. Kinda screwing with perfection. Besides, it would have been easier to date someone from LA/Miami/Dallas

HAHAHA!!! One of the funnier things I've heard today!

 

[troybilt]

Re: 360 bobber/Brat new tires update

Hey guys this is what makes this site soooo f'n awesome. I've learned so much. Thank you all for taking the time to look at this and break it down for me. It is so nice not to get back idot responses. I knew that the way that design worked it would not be the best because it articulated forward but I really didn't understand the full effect. So yeah guys, the information is awesome and I need to go back and read it a few more times so that I can absorb as much as I can.

Hey Chris I think chatting with Swagger is sound advice and if he doesn't mind I'd love to do so. Anyhow, I have access to some blueprints for a girder so I plan to look them over more throughly once I get the chance. So I'm sure I'll be looking for some advice.
Again, thanks for everything.
Troy

 

[troybilt]

Re: 360 bobber/Brat new tires update

... It's kinda like importing a Russian model and promptly taking her in for plastic surgery. Kinda screwing with perfection. Besides, it would have been easier to date someone from LA/Miami/Dallas

Hahaha, that's awesome Chris. Compliment taken. ;D

 

[troybilt]

Re: 360 bobber/Brat new tires update

Ok, I'd like to think out loud for a minute. See what you think. Hav I ben reedn right so far??
So, like I said, I've been doing a bunch of reading (I know that's dangerous) and I need to do a bunch more. But one thing I find interesting is the fact that hydraulic telescoping forks can change dynamic positive trail by as much as 2" during compression and extension. Of course there are variables to this such as rake and stem off set and so forth. I also find it interesting that a girder front end, if set up properly, is a better performing fork based on the fact that trail change can be limited to 3/16" over full cycle of max compression and max extension. I'm sure this statement is debatable depending on who you talk to. I should note that this is dynamic because it could still be set up an "x" amount of inches of static trail to begin with. In-fact it was stated in the literature that I read that many race engineers prefer developing a girder type set up over hydraulic telescoping forks for this and other reasons. ...Interesting.
Of couse they state the disclaimer that a poorly designed or poor built Girder can be real nightmare.

Anyhow, I've kind of given up on the design I posted above due to poor design but the literature I've read makes me interested to do a little measuring on that design just to see where it's at and how it acts.

Just glancing at it in the photos it looks as though the fork is set up with maybe a 1-1.5" of trail. The head tube is almost in line with the lower fork at the axle so it looks as though the rake was not change from the head tube angle. By looking at the bottome tree, I'm guessing that it has a stem off set of maybe 1-1.5" hence the 1-1.5" of static trail. So now if we are starting off with 1-1.5" of static trail that's within tolerance of being ok. I think the article states that about 5" of trail is optimun. Now if the shock used has a limited amout of travel, say 2" , I'm real curious as to what positive dynamic trail that translates to down at the axle. I suspect it will be outside of optimun specs but if it were..., say 4", then we would add the already 1-1.5" to come up with a total of 5.5" of total trail. So static trail would be 1-1.5" and dynamic trail would be 4". I know its not optimun but it kinda makes one think. Once I thought about it in these terms then I find it pretty interesting. I'm not sure I could do the math to figure out the arc of the lever from the pivot to obtain gained trail but I'd love to go measure it to see what its doing. Even if just for kicks :.

Ok, so please forgive me because I is still lernin and I'm trying to figure this all out.
Rake and trail info: http://64.172.168.34/neatstuff/rakeandtrail.htm
Girders: http://64.172.168.34/neatstuff/girder-1.htm

 

[doodL]

Re: 360 bobber/Brat new tires update

This is awesome ;D ;! I'm planning on building one when I get a bike!

 

[Kev Nemo]

Re: 360 bobber/Brat new tires update

These guys know a shitload about girders and choppers. Just don't post anything about building a Japanese bike-they're banned from there. :

http://www.jockeyjournal.com/forum/search.php?searchid=1618220&pp=25

 

[troybilt]

Re: 360 bobber/Brat new tires update

Hey Kev, thanks for the link. Unfortunately have to pass. I used to lurk there a lot until they did what they did to metric owners. Now I never go there. sorry don't mean to be a snob but...
Anyway, for bike building from scratch I think this site rocks: http://www.chopperweb.net/forum/index.php?s=
Seems like a great bunch to boot.

 

[biker_reject]

Re: 360 bobber/Brat new tires update

These guys know a shitload about girders and choppers. Just don't post anything about building a Japanese bike-they're banned from there. :

http://www.jockeyjournal.com/forum/search.php?searchid=1618220&pp=25

Now why would I want to visit a site like that???

 

[Tim]

Re: 360 bobber/Brat new tires update

Chopper Web looks like a good site - I'll have to sign up there.

 

[Kev Nemo]

Re: 360 bobber/Brat new tires update

Now why would I want to visit a site like that???

Well, fact is, the majority of knowledge on girder use is going to come from the traditional chopper community. Research is research.

 

[troybilt]

Re: 360 bobber/Brat new tires update

Chopper web you don't have to hide what you are building and compared to jockey it's like the difference between Chip Foose and Walmart Lube ;D Not quite that extreme but close

 

[troybilt]

Re: 360 bobber/Brat new tires update

I have a couple of quick updates. I've not made any decisions on new trees or girder for the winter part of the build. I did order a set of knee pads for the tank and more 2kclear. I plan to redo the tank and fender this winter. the tank has a couple of places but it seems that I'm the only one to notice. I'm going to re-do it because I'm just an anal sob ;D When I do, I'm considering adding an old school fuel gauge on the side of the tank out of brass and a clear tube. Once I repaint the tank I'll add the knee pads.
Also, Seems my fat arse is a little too much for the springs in their new position and the frame took off a little paint from the rear fender. I need to add a bigger bumpstop to the springs or get stronger springs. I would really like to get the stronger springs however, handling is really not that bad.

Ok, on to the bigger tires on factory rims saga. As most of you know I went way over the recommended sizes for my rims. I really need to put out a disclaimer on this because what Troy does is not always best for anyone else. So if you are new to riding please don't do this. I hate to generalize and I hate when other people do. But in this case I feel I probably should. However, I'm not your grandfather and I don't expect you to follow what I say just because I said it. I know that some of you are part of that new generation and I understand how most of you gather as much info as you can and make calculated decisions. So gather around my friends. This is just my take and my .02 so take it for what its worth.

First, A little history. I've been riding two wheels for a very very long time. I guess its been about 40 years. Jeez, I'm really old! (I really hate to sound like I'm blowing my own horn but feel it to be a little
necessary). It started when I was five with a minibike and I've not stopped riding since. I feel I can ride about anything no matter what it is. I laugh about the tires thing because hell, I'd ride the rims if someone told me not too. Yeah, I can be a little hard headed But at the same time it is all calculated and I know where my limits are and what the limits are of what I'm riding. If i don't, I feel confident in finding those limits. So that's who I am. That's why I am and why I have the attitude that I do. I hope i don't come across as arrogant. I just feel it is needed info that I hate to tell on me. And yes mom, I remember Indian Larry. I’ll be more careful. hahaha
A little more rant then onto the tires.
I also find it almost hilarious that we get stuck on all these 'numbers' when it seems there is no industry standard for tire sizes. I guess for the average Joe we have to take our bike to the stealership in order to get that critical size tire put on. Otherwise we have no idea if a replacement is the exact size that we are taking off. From what I can find it seems that the stealerships have the only true conversion charts. I'd love it if someone could produce a useable conversion chart.
The tires:
noticed little change on the back other than slightly less traction than I'd expect it should be. However the front at different pressures can be pretty different. Both tires have better traction than the 35 y/o dry rotted tires that i took off. So initially both tires were aired to about 32psi (if I remember correct) and were driven in different conditions and speeds. After getting a feel for the tires I had the bike to speeds of 85mph plus and everything in between mostly on curvy roads. Keep in mind that I was testing new suspension at the same time so it took me awhile to try different situations before becoming comfortable. Also keep in mind that I've experienced tank slappers at 145mph (not on this bike of course) and have a pretty good feel for their cause, yada, yada, yada... Also see history above. So anyhow, I've even felt comfortable enough to take a hand off the bar at any of those speeds. Sometimes I like to have a hand on the tank or sometimes I'd wave at passing bikers :. Keep in mind that I can be a little nutty. Again , see history above

Ok, so I aired the tires down just to see how they would respond. I think they were running about 22psi. The front wanted to walk on deceleration at different speeds. It was never too bad and slight acceleration always corrected. In fact I rode it like that for about a week. The back was nothing more than a little squishy at times. It just felt like i was running a low tire. However, because of the front I had to change the way I rode. The max speed with the deflated tires was about 65 -70mph. My guess is that most new riders would not feel comfortable in those situations and it would probably be pretty dangerous at best.
I'm now running the tires at about 32psi and have experienced no issues for my comfort level. As the tires wear that may change. Keep in mind what is right for me may not be right for you. Just because Troy jumps off the cliff doesn't mean that you will be ok doing so too.
EDIT: Sorry that ended up not being a quick update ;D

 

[JRK5892]

Re: 360 bobber/Brat new tires update

well said! Troy look at some sportster shocks, they are narrow like the ones you rock there and will give you a bit more umph in suspension... plus you can get them SUPER cheap on ebay... if you want a fatty look, you can toss on some stock street bob/dyna shocks, anything 06 and above will be a bit beefy(r) looking. what would really be trick is to get a set of air shocks off a touring harley, they have fittings on them that allow you to adjust the pressure and the comfort of the ride, you can get the 12 in ones on ebay for like 30 bucks, just make sure they have not been opened up and are just take offs. that is the best ride EVER! i had them on my harley for a while and it was like floating on air... LOVED IT...
you want to look for road king, ultra, any of the glides (road or street) and you will find good air shocks. the stock ones are what you want as they are a bit longer than the lowering shocks and wiht your kick out on your swing arm they will be perfect

you can typically get used ons for like 50 bucks. i then went to harley and got the shock fittings and hoses fro another 30 so that i could fill them both on one tube. worked awesome!


here are the dyna shocks off my harley that i am using on my bob if you want to go normal shocks... they are fatter so you will have to space them from your frame and swing arm rails... if you do not want to space them get some sportster shocks and they will be perfect!!!

 

[Swagger]

Re: 360 bobber/Brat new tires update

Hey Joe, great info on good cheap shocks for bobbers man! Love this joint!

Troy, well said regarding tire choices.

 

[troybilt]

Re: 360 bobber/Brat new tires update

Thanks guys.

Joe, that is some awesome info on the shocks! Thank you! I think for the way I ride I would need a pretty stiff set up and with those I could dial it in. Not to mention I'm going about 215 #these days :.
Anyhow, the issue at this point is I can't do much in the way of lengthing the upper shock mount bolts without some fab work that I don't want to get into. On the good side I think I would have plenty of clearance up there because of the way its set up. The bottom is where I might run into an isssue.

Well, I just noticed something. i see the shocks have an eye at the bottom and you just mounted the shock on the outside. That might give me enough room.

Ok ? for you. Did you have clearance issues at the bottom as well?
Thanks, Troy

 

[JRK5892]

Re: 360 bobber/Brat new tires update

clearance in reguards to what? i am going to have to make some spacers to move the shock out a bit yes, on the top by the frame i will weld the spacer on there, the botton one on the swing arm i will prob do the same once i figure out how far back i am going to go with the swing arm. my original plan was to kick the swing arm back enough to use sporty shocks on the inside of the frame rails, re locate my shock mounts on my swing arm... and run it like that... i still may, but as we where pulling the CB350 out of the back today so i can rip off the swing arm for chris.. my brother pointed out that without the shocks back there the little girl has no ass on her... i never thought of that... it looks weird almost... so i may have to keep the fatty shocks and keep them on the outside... went a bit off on a tangent there... sorry man... what where you wondering about clearance?
I am 225 so whatever i do has to be solid... doing my build cycle now and i am not going to get any smaller ;D

 

[troybilt]

Re: 360 bobber/Brat new tires update

Hahahha, I hear you on the "build" cycle. I always put on winter weight so I know a month from now I won't be the same too.

Glad to hear you are getting ready to work on the bob. I'm stoked to watch her progress. I agree, you gotta have a girl with an arse!

In the photo I can tell that with out the spacer the top of the shock might hit the frame. The upper shock mount on mine is different now. i may not need a spacer?? What do you think? I guess it's more the bottom that I'm wondering about.

 

[JRK5892]

Re: 360 bobber/Brat new tires update

well if you want to check... i can send you my shocks... ill send you the sporty and the dyna ones... take it for a rip and see what you think. i am not going to need them for a bit as i have to send the swing arm to chris and while it is gone i am going to rebuild the motor (for my first time total rebuild)
or i can just send one set... you tell me, either way i am fine with it... i am going to look man i may have an extra set of dyna shocks... but i doubt it... i have been coating them and selling them on ebay to make some extra $