How is BB height determined? Now I know it is from the ground to the BB, but if a certain frame was made for 1 3/8 rims, won't the BB height be lower with 1.5's?

I'm sure this is probably some dumb technical question that I don't need to know about, but just wondering

id like to know too...

I'm no expert but what you said above is exactly correct. You have to look at the bike manufacturers specs. The frames are sized for certain tire sizes. This is important for where the brake posts are set. The manufacturer should be able to tell you what size tires the bike was set up for. When they list a particular bb height, it was spec'd with a certain size tire.

Brad

Brad,

I don't know if you saw my other posts, but I found out about the tires the hard way! I had to get the Bombshell adapters and they were a pain in the rear to get set up and there isn't a lot of room to adjust them.

I also posted sometime ago about the fact that I had called a few shops that sold the Intense frame and asked about switching the parts over from his Redline. They said everything would work fine, which wasn't the case and like you said, I wish that someone would state what size tires the frames were desingend for.

I'm new to this stuff, so I figured a Redline Expert frame and an Intense expert frame would accept the same size parts, but I was wrong.

My ? about the BB height though is becasue I am wondering now if my son has the same ground clearance as he did with the Redline. If it is a lot lower on the Intense due to the fact that I used the 1.5 rims, I'm worried he may clip his pedals while pedaling over things he had no problem before.

Can anyone tell me just how many inches bigger around a 1 3/8 rim is to the 1.5 ?

Think of it like this. A 20x1.75 with the tire mounted is actually a bit closer to the same overall height of a 20x1.3/8 with the tire mounted then you might think. Even though the rims them selves are much different. A 1 3/8 rim is larger and the tire is smaller, a 1.75 rim is smaller and the tire is larger. The big difference is the breaks… good luck.

Go Ahead shoot… I am use to it. Ziggy

Ziggy,

Where does a 1.5 rim fit between the others? My son has run both a 1.5 tire and a 1.75 tire on those rims, hasn't figured out what he likes better, but as far as the size of the rim, I have no idea what a 1.75 looks like compared to any other size.

The only reason I know the 1 3/8 is larger than what he has ,is that the guy at the bike shop pulled one out and held it next to the 1.5 for me.

I did measure his BB height now with the 1.5 rims on it and it is an inch and a half lower than when he had the redline frame. I hope this isn't going to mess things up to bad.

I'm not into all this tecnical stuff, we just started this stuff last year and this is the first bike we have(with the help of my pal LeadSled ) put together.

The Redline came complete, so I didn't have to worry about that.

I'll be totally honest, I don't really know what kind of difference he is going to get from swithching to the Intense frame from the Redline, other than the Intense seemed a lot lighter.

He just asked to try something new, and Intense was suggested by a lot of people.