I have a triple on my road bike and I can't get it on the big cog, even while on the small chainring. Adjusting the low gear limit screw on the RD doesn't seem to do anything.

Any suggestions?

thanks,

Cliff

Sounds like the cable doessn't have enough tension.
When on the smallest rear cog, there shouldn't be tension on the cable, but there should be NO slop either.

Sounds like an issue with the cable tension as stated above. If that doesn't work, make sure the limiter screws aren't set too far (i know you said you did it but, it may have become an issue without you knowing it while playing with the cable tension) Also, are these friction shifters, grip, indexed, and trigger? If they are grip or trigger, i've found that sometimes you have to over shoot a bit to get it to shift into the largest cogs and chainrings... however be careful as it may end with the derailure in the wheel if the limit screws aren't set properly

Thanks for the advice, but I thought that the cable tension is set when the chain is in the big chainring and small cog. I'm having the problem when I'm in the small chainring and big cog.

When I'm in the secong biggest cog and when I push the brifter to get to the largest cog. it seems to go halfway there and never moves the chain completely over. When I release the pressure on the brifter it goes back to the second largest cog. It seems to make sense that this is a limit screw setting, but like I said, it doesn't seem to make a difference.

Thanks again,

Cliff

Try turning the barrel adjuster at the rear derailleur 1/2 turn, or so, counter-clockwise. If you go too far you'll have trouble shifting to the smallest cog.
Be certain sure that you have not backed out the low limit screw too far, this could cause serious damage. Go to https://www.parktool.com for derailleur adjustment instructions. These are also available at https://shimano.com.

Al

https://www.parktool.com/repair/readhowto.asp?id=64

Do this adjustment from the beginning and get back to us.

That's what she said ;-)))))

I went thru the whole procedure and it's the same.

I did learn something - I can get to the big cog if I just pull on the cable, but if I use the brifter it (the brifter) only moves so far until it feels like it's blocked and it only gets to the second largest cog.

This sounds as if the shifter was not in its highest position with the cable all the way out when the cable was attached to the rear derailleur.
Shift to the smallest cog. Detach the cable. Pull on the free end of the cable while working the small shift lever several times. Then re-attach the cable with no slack. Adjust the cable tension with the barrel adjuster (probably counter-clockwise) as needed.