On https://www.logainm.ie/en/1165655 there is link to a sound file with the pronunciation of Caher. It sounds to me pretty much like the English word 'care'. On my Michelin-map Caher is not spelled with an e but with an i: Cahir. First question: does this matter where the pronunciation is concerned? In other words: Is there a difference in the pronunciation of Caher and Cahir?

Second question. The word Caher can also be found in the place name Cahersiveen. Am I right that the pronunciation of Caher in Cahersiveen is different from Caher (=Cahir)? And that Caher in Cahersiveen is pronounced in two syllables?

Thanks in advance.

That's right. How Cahir/Caher is pronounced "Care" in English.

How the element "Cahir/Caher" i pronounced in English in Irish Town names often depends on the local dialect and the specifics of how Irish decayed among the last few bilingual speakers.

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The dialect I use is Cork Irish.
Ar sgáth a chéile a mhairid na daoine, lag agus láidir, uasal is íseal

English place names are often pronounced differently despite of similar spelling.
https://www.logainm.ie/en/1165655 is Caher, Co. Tipperary
Compare with Caher, Co. Kerry (the civil parish in which Cahersiveen is situated)
https://www.logainm.ie/en/1061
or with Caher, Co. Limerick
https://www.logainm.ie/en/1373777
Caher, Co. Laois
https://www.logainm.ie/en/1373503
Caher, Co. Clare
https://www.logainm.ie/en/1371862
Only in Caher, Co. Tipperary the pronunciation is like "care" /keə(r)/, everywhere else /kahər/

Note the interesting parallel with Welsh "caer"

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